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April 2011

         Virtual Mainframe –
Legacy Application Rehosting

                   Santosh Kumar
                    Vishnu Prasad
Virtual Mainframe - Legacy Application Rehosting | April 2011




Contents
Introduction	                                                                                                                   2

Mainframe Migration Options	                                                                                                    3

Application Rehosting	                                                                                                          4

Application Rehosting Process	                                                                                                  9

End Notes	                                                                                                                    11

Appendix – A	                                                                                                                 12

References	                                                                                                                   13

About the Authors	                                                                                                            13

About HCL	                                                                                                                    14




Introduction

Back‑ground
From the mid 1950’s, Mainframes have been the main stay for
organizations enabling them to integrate all their data processing
requirements and applications into a single, robust management
information system. Around the same time COBOL was developed
with the aim of making it easy to write business applications.
This early beginning and widespread adoption of Mainframe
hardware with COBOL applications running on them has led to
the current scenario where almost all organizations have at least a
part of their business IT requirements being addressed by ‘Legacy
Systems’. Significantly, these ‘Legacy Systems’ handle core business
functionalities and are characterized by large application sizes and
high complexity.

Rise of the Alternatives
Starting with the 1970’s and 80’s, the world of computing
saw the conception and rise of alternate computing platforms
like UNIX, Linux and Windows where the emphasis was on
flexibility, interoperability, application portability and standards
compatibility. This also sparked the evolution and rise of various
languages, programming paradigms, application architectures and
communication protocols. The advent of these more modern
application languages and powerful, flexible computing platforms
has provided organizations with cheaper and comparably powerful


© 2011, HCL Technologies. Reproduction Prohibited. This document is protected under Copyright by the Author, all rights reserved.
Virtual Mainframe - Legacy Application Rehosting | April 2011




alternatives to run their business applications. They now had
different options to choose from for their IT infrastructure
beyond Mainframes.

Inertia
The availability of options doesn’t automatically result in the use
and adoption of the same. Factors like business criticality, existing
technical complexity of the ‘Legacy Applications’, the innate risk
averseness of organizations and, in certain instances, the outright
superiority of the mainframes have resulted in their persistence as
the pre-dominant IT platform in spite of growth in the number
of replacement options. As a consequence of this inertia against
new platforms, the Mainframe has evolved into a niche but
monopolistically controlled platform with unrealistic licensing
costs and methods.

The Need for Migration
At present, in a post recessionary world, organizational IT is driven
as much by the need to improve Total Cost of Ownership (TCO) and
Return on Investment (ROI) as it is by technical and performance
characteristics. Now, organizations are keen to explore avenues
which enable them to decrease costs while retaining functionality,
meeting SLAs and mitigating risk. The main approach for realizing
this, by migrating their existing legacy applications and functionality
to alternate server environments which offer greater economies
of scale and increased business flexibility, has increasingly gained
credibility among organizations as this enables them to reduce
overall expenditures while allowing them to leverage their existing
systems in new ways to open up opportunities for increased
IT value.

Mainframe Migration Options
Migrating out of mainframes can be accomplished in multiple ways,
the main ones being:

Application Re-engineering
This approach involves partial or complete redesign of the
application architecture and re-writing the application to fit into this
new architecture. It results in an efficient and optimized solution
for the platform it is being targeted at but is heavily dependent
on the functionality of the current application being completely
understood and exactly replicated. This approach usually involves
taking advantage of modern programming languages, tools and
methodologies to transform and recode the existing functionality.

Application Replacement
This approach involves replacing the existing application and its
functionality with a ready-made solution package, also referred to
as ‘Commercial-off-the-Shelf’ solution (COTS). ‘Replacement’ is a
viable option when the ‘COTS’ already has all of the functionality
being delivered by the existing application and is available for the
target platform being considered. In practice, however, no COTS

© 2011, HCL Technologies. Reproduction Prohibited. This document is protected under Copyright by the Author, all rights reserved.
Virtual Mainframe - Legacy Application Rehosting | April 2011




product will be able to provide an exact functionality match and
would thus require varying degrees of customization and testing
before it can be rolled-out for general use.

Application Rehosting
This approach involves changing hosts or platforms on which the
application runs. However, unlike the other methods, the software
application being rehosted doesn’t undergo major change in how
the end users use it. This ability to enable an existing application
to be run ‘As-Is’, on the target platform ensures that Rehosting
removes the risk associated with adopting a new platform for
existing application functionality and at the same time brings
the benefits of moving to a new platform in terms of flexibility
and cost.

Migration Option Comparison
When compared based on parameters like Migration Cost,
Migration Time, Time for realizing ROI, Skills required to work on
the Migrated platform, Migration Risks, Innovation in the process
and Ability to Extend the application on the target platform, the
various migration options stack up as follows:

                            Re-engineer                       Replace                            Rehost
 Cost                       High                              High                               Moderate to Low

 Time                       High                              High to Moderate                   Low

 ROI                        Moderate                          Slow                               Fast

 Skills                     Re-train                          Re-train                           Retain

 Risks                      Moderate                          Moderate                           Low

 Innovation                 High                              Moderate                           Low

 Extensibility              High                              High to Moderate                   Moderate

Table A - Migration Option Comparison


If organizations need a quick turnaround on their mainframe
migration activity, a lower TCO and faster ROI in the migrated
solution, it is clear that Rehosting is the way to go.

Application Rehosting

What it Entails
Application Rehosting involves moving the application portfolio
– everything that makes up the application’s eco-system like
application code and logic, data, scripts, screens etc. – from the
mainframe to the new platform with minimal or no changes. It
preserves current business rules, procedures and functionalities
and causes minimal disruption to how the end-user interfaces with
the application.




© 2011, HCL Technologies. Reproduction Prohibited. This document is protected under Copyright by the Author, all rights reserved.
Virtual Mainframe - Legacy Application Rehosting | April 2011




Target Platforms
The availability of multiple computing platforms in the market has
meant that there are many target platform options to choose from
based on organization specific business needs and strategy. The
choice of computing platforms includes:

 Hardware Platforms Wintel, x86, SPARC, Itanium
 Operating Systems                          Windows, UNIX, Linux

 Emulation Layers                           .NET, JVM

Table B: Target platform options for rehosting

Types of Rehosting
The major components that make up any legacy application are
the programs, batch scripts, UI components, files and tables.
Apart from these the eco system also consists of components like
control cards and configuration files. On the basis of how these
source components are handled during rehosting to a target
platform, there are two main ways via which application rehosting
can be achieved.
Retaining the Technology Stack
This method makes sure that the change required in the existing
technology stack of the application during rehosting is minimum,
thereby eliminating risk to a high degree and greatly reducing the
time taken for the migration. To achieve all this, it necessitates the
presence of an Application Execution Environment (usually in the
form of a software emulation layer) that provides behavior and
technology support similar to the source mainframe. However,
this method uses the target platform environment merely as a
foundation for the emulation layer and doesn’t immediately exploit
the features of the environment for the application. Usually, in this
method of rehosting, the task of altering the technology stack is
taken up as a follow-up/ phase-2 activity.
Altering the Technology Stack
This method ensures that the way the end-users interact with
the application and application functionality remains unchanged
but changes a few components in the technology stack to take
advantage of the target platform environment. For example, JCLs
are converted to Shell Scripts; BMS Maps are converted to .NET
screens etc. However, the technology conversion makes this method
inherently more risky and would require more effort and time spent
on risk mitigation efforts when compared to the previous method.
Proven emulation platforms, tools and techniques by multiple
vendors are available for rehosting of either type.
(Refer to Appendix-A for a comparison between some of the main
players in this space).

When to choose Rehosting
All Legacy Applications are not automatically suited for rehosting.
The choice of migration strategy depends on various factors like


© 2011, HCL Technologies. Reproduction Prohibited. This document is protected under Copyright by the Author, all rights reserved.
Virtual Mainframe - Legacy Application Rehosting | April 2011




the size, complexity and criticality of the applications and systems
in consideration.
For e.g., SMEs (Small and Medium Enterprises), could very well
apply Rehosting as a Mainframe Replacement strategy, because
all of their applications might fit cleanly into a non-mainframe
platform. On the other hand, in case of Large Mainframe shops,
rehosting of non-critical work off the mainframe can free up the
MIPS for more critical data processing needs and also help defer
their mainframe upgrade plans thereby benefitting from a hybrid
Mainframe + Rehosting solution.
They main factors that need to be considered are:
 Technology Factors                                               Business Factors
 The availability of an Execution En-                             Organization’s technology roadmap
 vironment for the technology stack                               and business plans that the Legacy
 on the preferred target platform                                 Application must cater to

 The proportion of the technology                                 Business criticality of the
 stack that is not readily Rehostable                             Legacy Application
 and requires some change

 The availability of options to port or                           Current TCO of the mainframe
 replicate the existing eco-system                                and the potential reduction in cost
 on the preferred target platform                                 (TCO) which can be achieved

 Size of the mainframe, in MIPS,                                  The time period in which cost
 that is being targeted for migration                             reduction can be achieved (ROI)

Table C: Factors influencing migration options
As a thumb rule, ‘Rehosting’ can be a viable solution where
•	 Legacy Application has a fairly standard mainframe technology
   stack (COBOL, PL/1, CICS, JCL, VSAM, GDG, DB2, IMS,
   BMS)
•	 The mainframe MIPS consumption costs are disproportionately
   higher compared to associated business value which is derived
   from the mainframe
•	 Quick turn-around is required for the migration

Rehosting Benefits
The benefits that Application Rehosting brings to the table can be
categorized as below:
Continuity
It allows organizations to continue using the stable applications
that they have relied upon for long, since it involves using the
same application and technology stack but on a different platform.
Extensive retraining of valuable personnel is eliminated and current
skill sets can be reused. This minimizes disruptions to existing teams
and workflows.
Low Risk
Since the amount of change required in the application is
comparatively minimal or non-existent (as against COTS or
Re-engineering), this exercise is ‘low risk’ by definition.


© 2011, HCL Technologies. Reproduction Prohibited. This document is protected under Copyright by the Author, all rights reserved.
Virtual Mainframe - Legacy Application Rehosting | April 2011




Low Cost
The costs involved in procuring, operating and upgrading the target
platform, in terms of hardware as well as software, are substantially
lower when compared to the costs incurred for the equivalent
components on the Mainframe. This results in huge cost savings for
the organization post-Rehosting, with typical ROI within 18 to 24
months. It also significantly reduces cost of operations, freeing up
the IT budget for full modernization and innovation.
Less Effort
ince most of the application technology stack is retained, existing
development and maintenance resources can be reused with
minimal retraining. It also ensures that end-users are not faced with
any radically new way of interacting with the application, thereby
reducing end-user re-training efforts.
Scalability
Rehosting to a modern target platform provides the organization
with the ability to scale the system up or down based on their
load and growth. But more importantly, it opens the possibility of
horizontally scaling out their application servers into a ‘cluster’.
Flexibility
Because the applications are now running on modern platforms,
they can often be easily wrapped in a powerful GUI as opposed
to the traditional character-based UI. This also makes it easier and
cheaper to extend the existing applications with a Web Services
front-end than when they were running on the mainframe.

Rehosting vs. Other types of Migration
Rehosting is inherently different from other types of Migration
because:
•	 It involves moving the existing application to the target platform
   with minimal or no changes to the way it currently exists and
   behaves whereas other migration options involve changing the
   entire application architecture, technology stack and usability
•	 It requires the availability of compilation and run-time support
   for mainframe application source and data on the target platform
   whereas other option involve using the native environments
   available on the target platform
•	 It mainly addresses the high costs and inherent inflexibility of
   running Legacy Applications while reducing risks involved in
   moving to a cheaper platform whereas other migration options
   usually address the challenges related to application code quality
   and architecture also
•	 It is largely tool driven and achieves the porting and execution
   of Legacy Applications on the new platform with a high degree
   of automation whereas other options are comparatively more
   manual-work intensive and time consuming




© 2011, HCL Technologies. Reproduction Prohibited. This document is protected under Copyright by the Author, all rights reserved.
Virtual Mainframe - Legacy Application Rehosting | April 2011




Rehosting – Reference Architecture

                                                                                                             UI Layer

                                                                                                            IMS Screens
                                                                       3270                                                            BMS
                                                                                                               Others


                                                                                                         Batch Layer (JES)

                               JCL/ PROC/ other CL                                                              Job Scheduler (CA-7/-11 etc.)

                                      Third party Utilities                                                        IBM Utilities (IEBCOPY,
                                       (Sync SORT etc.)                                                               IEBGENER etc.)




                                                                                                                                                         RACF, CA Top Secret, ACF2 etc.
                                                                                                            Data Layer




                                                                                                                                                                                          Security Layer
                                      Indexed                                                                       DB2/ IMS
                                                                                                       GDG                            Flat Files
                                        Files                                                                        DB etc.


                                                                                                         Application Layer

                                                                                              4GL                             3GL

                                              X Gen                                             Pac Base           Business          Business
                                                                                                                   Logic in          Logic in
                                      CA Ideal                                                      Other          COBOL               PL/1


                                                                                              Assembler, REXX, DYL280, SAS etc.


                                                                                                       Transaction Layer

                                                                                CICS TS                        IMS DC                Other


                                                                                               z/OS, OS390, Bull etc.




                                                                                                                         UI Layer
                                                                                                  3270               IMS Screens                    BMS

                                                                                                 JSP            HTML            .NET           Web Services


                                                                                                    Batch Layer (Emulated JES/ OS Layer etc.)
                                      Active Directory, OpenLDAP, Other LDAP based products




                                                                                              JCL/ PROC/ shell Scripts/       Job Scheduler (Autosys,
                                                                                                      Perl ....                   BMC Control...)

                                                                                                             Equivalent 3rd party utilities


                                                                                                                        Data Layer
                     Security Layer




                                                                                               Indexed                         RDBMS
                                                                                                                 GDG         Oracle, DB2 SQL       Flat Files
                                                                                                 Files                          Server etc.



                                                                                                                  Application Layer

                                                                                                         4GL                              3GL
                                                                                                                              Business          Business
                                                                                                   Converted to
                                                                                                                              Logic in          Logic in
                                                                                                  supported 3GL
                                                                                                                              COBOL               PL/1

                                                                                                     Converted to equivalent in supported 3GL


                                                                                                                  Transaction Layer

                                                                                                    Emulated CICS/ IMS DC/ OLTP environments


                                                                                                       Windows, UNIX, Linux


Figure 1 - Generic Rehosting Reference Architecture


© 2011, HCL Technologies. Reproduction Prohibited. This document is protected under Copyright by the Author, all rights reserved.
Virtual Mainframe - Legacy Application Rehosting | April 2011




Application Rehosting Process
Legacy applications usually exist within an ecosystem of interfaces,
tools and utilities on the mainframe which they actively interact
with. Legacy applications, in general, also do not exist on the
mainframe in isolation and as such share certain application assets
and the mainframe resources with other applications. The presence
of such interactions and dependencies makes it imperative that any
rehosting exercise focuses on not just the application inventory but
also on providing a similar eco-system on the target platform for
the application to run in.
In order to achieve that, the process of Rehosting should usually be
as indicated:
                                                General Assessment

                                               Inventory Assessment

                                                 Rehosting Strategy

                                                    Platform Setup

                                                    Pilot Rehosting

                                                Complete Rehosting

                                                           Testing

                                                             UAT

                                                          Go-Live

Figure 2 – Rehosting Process

General Assessment
This is the beginning of the process where the existing application
on the mainframe is assessed to understand the following:
Technology stack
This includes identifying programming languages, scripting
languages, transaction processing environments, batch and online
technologies, files types, data types, database types and utilities.
Application Environment
This includes identifying processes for backups, archiving and DR,
identifying application interfaces, character sets, compiler options,
identifying batch scheduling, security and access management
requirements and identifying utilities and third party tools
being used.
Usage and Performance
This includes identifying application usage patterns, application
load characteristics, application response times and base lining the
performance of the application in its current state.



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Virtual Mainframe - Legacy Application Rehosting | April 2011




Non-Performance Parameters
This includes identifying the requirements – existing as well as
future – for application availability, scalability, modification
and extensibility.

Inventory Assessment
The general assessment is followed by a detailed inventory
assessment. This is required in order to obtain:
Size of application
In terms of number of components and complexity of components.
Technology Grouping
Grouping of the components in terms of their technology to
understand the size and proportion of each technology in the
over-all technology stack.

Rehosting Strategy
The results of the assessment enables the formation of the rehosting
strategy which consists of:
•	 Choice of rehosting environment vendor
•	 Strategy to handle un-supported technologies
•	 Environment mapping
•	 Target Architecture, Sizing and Workflow

Rehosting Environment Setup
This is where the target platform is built for the first time and
configured as per the decided architecture.

Pilot Rehosting
As the saying goes, “The proof is in the pudding”. Having done
the assessment and developed a strategy for the rehosting based on
that definitely makes the exercise proceed smoothly and quickly
but doesn’t provide a 100% guarantee that the strategy will succeed
completely in meeting all the requirements. In order to save time,
effort and costs, it is advisable to put the rehosting strategy to test
by means of a Test run or Pilot done on a small, representative
subset of the application. This will help identify any shortfalls in the
overall rehosting strategy which can then be rectified accordingly.

Rehost the complete application
Once the strategy has been tested and perfected via the Pilot, the
entire application – programs, scripts, screens, data, tools and
utilities – can then be rehosted to the target platform in a smooth
and efficient manner.

Post-Rehosting Testing
By definition, rehosting provides the same functionality of the
legacy application on the target platform. Hence the focus of the


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11
Virtual Mainframe - Legacy Application Rehosting | April 2011




testing effort in a typical rehosting exercise would be around the
non-functional aspects like performance, stability and availability.
Functional regression testing will also be carried out.

UAT/ Parallel Run/ Field Testing
In this phase, the target platform will be configured in the same way
as it would eventually be as a live system and will be run alongside
the mainframe. As much as possible, the same data will be used
on both the platforms and end-users would be invited to use the
rehosted platform. Using the new platform in a production like
environment helps identify any final wrinkles in the rehosting
strategy and eliminate them.

Go-live
The final phase, where the new target platform takes the place of
the mainframe as the application platform.

Training
As a parallel activity which can be taken up along with any of the
testing phases, training activities have to be started for the various
teams that would be using the new platform. This includes:
Application team
They have to be trained in working with new IDEs which will
be used for ongoing application development and maintenance
activities.
Administration team
They have to be trained in the administration of the various
components that make up the new application ecosystem.

Decommissioning  Modernization
Once the new platform is in place, plans for decommissioning the
application from the mainframe as well as for modernizing and
extending the rehosted application can be worked on.

End Notes
One size doesn’t fit all in the context of legacy modernization.
There is no single, pre-packaged solution that is right for everyone
seeking to modernize their existing mainframe applications.
While the traditional legacy modernization and migration methods
have their place, “Legacy Rehosting” makes a strong case for itself as
a viable modernization solution because of the benefits it provides in
terms of reduced migration risk, short implementation time frame,
faster ROI and greatly reduced TCO. “Legacy Rehosting” works
for enterprises irrespective of their mainframe footprint. It can
be leveraged either to completely replace their mainframes or for
partial workload offloading from the mainframe. In either case the
end result is a sizable reduction in their overall mainframe costs.




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12
Virtual Mainframe - Legacy Application Rehosting | April 2011




Appendix – A
                              TP  BP                                                                       Other
                              engines                           Appli‑                                     tools
                                                                          Data
                     Platform Runtime                            cation                                     (Monitor‑
                                                                          Support
                              environ‑                           handling                                   ing, Secu‑
                              ment                                                                          rity etc.)
 Microfo‑ Windows                        Server       Minimal                         ISAM                  Via 3rd
 cus      UNIX                           Enterprise   to No                           GDG                   Party
          Linux                          Edition (for change
                                                                                      Any
                                         TPE  BPE)
                                                                                      RDBMS
                                         MFCOBOL
                                         Runtime
 Clerity             Windows             UniKix TPE              Minimal              ISAM                  Provides
                     UNIX                UniKix BPE              to No                Oracle,               Monitoring,
                     Linux                                       change               DB2 UDB               Security
                                         vCOBOL
                                                                                                            and Access
                                         Runtime
                                                                                                            mgmt. All
                                                                                                            others via
                                                                                                            3rd Party
 Oracle              UNIX                Tuxedo as   JCL       ISAM                                         Via 3rd
 Tuxedo              Linux               TPE         converted Oracle,                                      Party
                                         OS Shell as to shell  DB2 UDB
                                         BPE         scripts
                                         MFCOBOL                 BMS
                                         or Net-                 converted
                                         COBOL                   to JSP/
                                                                 HTML
 Fujitsu Windows                         NeoKicks                BMS                  Convert               Via 3rd
 Alchemy                                 and .NET                converted            indexed               Party
                                         NeoBatch                to ASP.              file to
                                                                 NET                  tables
                                         NetCOBOL
                                         Runtime                                      Any
                                                                                      RDBMS
 COBOL-              Windows             XCICS                   JCL                  VSAM                  Provides
 IT                  UNIX                XeBE                    converted            Emulation             Schedul-
 HTWC                Linux                                       to shell             Any                   ing. All
                                         COBOL-IT
                                                                 scripts              RDBMS                 others via
                                         or Net-
                                                                                                            3rd Party
                                         COBOL
 TMax‑               UNIX                Open-                   Minimal              VSAM                  Via 3rd
 Soft                Linux               FRAME (for              to No                Emulation             Party
                                         TPE and                 change               Any
                                         BPE)                                         RDBMS
                                         Own
                                         COBOL
                                         Runtime
 IBM TX-             Windows             TX-Series               JCL                  VSAM                  Via 3rd
 Series              UNIX                (CICS) as               converted            Emulation             Party
                     Linux               TPE                     to shell             Any
                                         No JCL                  scripts              RDBMS
                                         support
                                         MFCOBOL
                                         or Net-
                                         COBOL


***Click on the vendor name for the website


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Virtual Mainframe - Legacy Application Rehosting | April 2011




References
1. Wikipedia
	 http://en.wikipedia.org/wiki/History_of_IBM_mainframe_
  operating_systems

2. The History of Computing Project
	 http://www.thocp.net/hardware/mainframe.htm

3. IBM
	 http://www-03.ibm.com/ibm/history/exhibits/mainframe/
  mainframe_intro.html

4.	University of Maryland, Baltimore County
	 http://www.cs.umbc.edu/courses/graduate/631/Fall2002/
  COBOL.pdf

5. Microsoft
	 http://www.microsoft.com/downloads/en/details.
  aspx?FamilyID=1637d24d-fb67-4d6e-adc7-e101981c728bdispla
  ylang=en




About the Authors
Santosh Kumar is a Mainframe migration/modernization architect
with the HCL Mainframe Solutions Centre of Excellence. He has
around 10 years of Mainframe development and solutions experience
and has been involved in architecting multiple large scale legacy
modernization programs.
Vishnu Prasad is a Senior Project Manager handling Legacy
Application Rehosting with the HCL Mainframe Solutions Centre
of Excellence. He has around 10 years of Mainframe development
and modernization solutions design experience.




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Virtual Mainframe - Legacy Application Rehosting | April 2011




About HCL

HCL Technologies
HCL Technologies is a leading global IT services company, working
with clients in the areas that impact and redefine the core of their
businesses. Since its inception into the global landscape after its
IPO in 1999, HCL focuses on ‘transformational outsourcing’,
underlined by innovation and value creation, and offers integrated
portfolio of services including software-led IT solutions, remote
infrastructure management, engineering and RD services and
BPO. HCL leverages its extensive global offshore infrastructure
and network of offices in 26 countries to provide holistic,
multi-service delivery in key industry verticals including
Financial Services, Manufacturing, Consumer Services, Public
Services and Healthcare. HCL takes pride in its philosophy of
‘Employee First’ which empowers our 72,267 transformers to
create a real value for the customers. HCL Technologies, along
with its subsidiaries, had consolidated revenues of US$ 3.1 billion
(Rs. 14,101 crores), as on 31st December 2010 (on LTMbasis).


About HCL Enterprise
HCL is a $5.5 billion leading global technology and IT enterprise
comprising two companies listed in India - HCL Technologies
and HCL Infosystems. Founded in 1976, HCL is one of India’s
original IT garage start-ups. A pioneer of modern computing, HCL
is a global transformational enterprise today. Its range of offerings
includes product engineering, custom  package applications,
BPO, IT infrastructure services, IT hardware, systems integration,
and distribution of information and communications technology
(ICT) products across a wide range of focused industry verticals.
The HCL team consists of over 79,000 professionals of diverse
nationalities, who operate from 31 countries including over
500 points of presence in India. HCL has partnerships with several
leading Global 1000 firms, including leading IT and technology
firms. For more information, please visit www.hcl.com.

© 2011, HCL Technologies. Reproduction Prohibited. This document is protected under Copyright by the Author, all rights reserved.

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HCLT Whitepaper: Virtual Mainframe

  • 1. April 2011 Virtual Mainframe – Legacy Application Rehosting Santosh Kumar Vishnu Prasad
  • 2. Virtual Mainframe - Legacy Application Rehosting | April 2011 Contents Introduction 2 Mainframe Migration Options 3 Application Rehosting 4 Application Rehosting Process 9 End Notes 11 Appendix – A 12 References 13 About the Authors 13 About HCL 14 Introduction Back‑ground From the mid 1950’s, Mainframes have been the main stay for organizations enabling them to integrate all their data processing requirements and applications into a single, robust management information system. Around the same time COBOL was developed with the aim of making it easy to write business applications. This early beginning and widespread adoption of Mainframe hardware with COBOL applications running on them has led to the current scenario where almost all organizations have at least a part of their business IT requirements being addressed by ‘Legacy Systems’. Significantly, these ‘Legacy Systems’ handle core business functionalities and are characterized by large application sizes and high complexity. Rise of the Alternatives Starting with the 1970’s and 80’s, the world of computing saw the conception and rise of alternate computing platforms like UNIX, Linux and Windows where the emphasis was on flexibility, interoperability, application portability and standards compatibility. This also sparked the evolution and rise of various languages, programming paradigms, application architectures and communication protocols. The advent of these more modern application languages and powerful, flexible computing platforms has provided organizations with cheaper and comparably powerful © 2011, HCL Technologies. Reproduction Prohibited. This document is protected under Copyright by the Author, all rights reserved.
  • 3. Virtual Mainframe - Legacy Application Rehosting | April 2011 alternatives to run their business applications. They now had different options to choose from for their IT infrastructure beyond Mainframes. Inertia The availability of options doesn’t automatically result in the use and adoption of the same. Factors like business criticality, existing technical complexity of the ‘Legacy Applications’, the innate risk averseness of organizations and, in certain instances, the outright superiority of the mainframes have resulted in their persistence as the pre-dominant IT platform in spite of growth in the number of replacement options. As a consequence of this inertia against new platforms, the Mainframe has evolved into a niche but monopolistically controlled platform with unrealistic licensing costs and methods. The Need for Migration At present, in a post recessionary world, organizational IT is driven as much by the need to improve Total Cost of Ownership (TCO) and Return on Investment (ROI) as it is by technical and performance characteristics. Now, organizations are keen to explore avenues which enable them to decrease costs while retaining functionality, meeting SLAs and mitigating risk. The main approach for realizing this, by migrating their existing legacy applications and functionality to alternate server environments which offer greater economies of scale and increased business flexibility, has increasingly gained credibility among organizations as this enables them to reduce overall expenditures while allowing them to leverage their existing systems in new ways to open up opportunities for increased IT value. Mainframe Migration Options Migrating out of mainframes can be accomplished in multiple ways, the main ones being: Application Re-engineering This approach involves partial or complete redesign of the application architecture and re-writing the application to fit into this new architecture. It results in an efficient and optimized solution for the platform it is being targeted at but is heavily dependent on the functionality of the current application being completely understood and exactly replicated. This approach usually involves taking advantage of modern programming languages, tools and methodologies to transform and recode the existing functionality. Application Replacement This approach involves replacing the existing application and its functionality with a ready-made solution package, also referred to as ‘Commercial-off-the-Shelf’ solution (COTS). ‘Replacement’ is a viable option when the ‘COTS’ already has all of the functionality being delivered by the existing application and is available for the target platform being considered. In practice, however, no COTS © 2011, HCL Technologies. Reproduction Prohibited. This document is protected under Copyright by the Author, all rights reserved.
  • 4. Virtual Mainframe - Legacy Application Rehosting | April 2011 product will be able to provide an exact functionality match and would thus require varying degrees of customization and testing before it can be rolled-out for general use. Application Rehosting This approach involves changing hosts or platforms on which the application runs. However, unlike the other methods, the software application being rehosted doesn’t undergo major change in how the end users use it. This ability to enable an existing application to be run ‘As-Is’, on the target platform ensures that Rehosting removes the risk associated with adopting a new platform for existing application functionality and at the same time brings the benefits of moving to a new platform in terms of flexibility and cost. Migration Option Comparison When compared based on parameters like Migration Cost, Migration Time, Time for realizing ROI, Skills required to work on the Migrated platform, Migration Risks, Innovation in the process and Ability to Extend the application on the target platform, the various migration options stack up as follows: Re-engineer Replace Rehost Cost High High Moderate to Low Time High High to Moderate Low ROI Moderate Slow Fast Skills Re-train Re-train Retain Risks Moderate Moderate Low Innovation High Moderate Low Extensibility High High to Moderate Moderate Table A - Migration Option Comparison If organizations need a quick turnaround on their mainframe migration activity, a lower TCO and faster ROI in the migrated solution, it is clear that Rehosting is the way to go. Application Rehosting What it Entails Application Rehosting involves moving the application portfolio – everything that makes up the application’s eco-system like application code and logic, data, scripts, screens etc. – from the mainframe to the new platform with minimal or no changes. It preserves current business rules, procedures and functionalities and causes minimal disruption to how the end-user interfaces with the application. © 2011, HCL Technologies. Reproduction Prohibited. This document is protected under Copyright by the Author, all rights reserved.
  • 5. Virtual Mainframe - Legacy Application Rehosting | April 2011 Target Platforms The availability of multiple computing platforms in the market has meant that there are many target platform options to choose from based on organization specific business needs and strategy. The choice of computing platforms includes: Hardware Platforms Wintel, x86, SPARC, Itanium Operating Systems Windows, UNIX, Linux Emulation Layers .NET, JVM Table B: Target platform options for rehosting Types of Rehosting The major components that make up any legacy application are the programs, batch scripts, UI components, files and tables. Apart from these the eco system also consists of components like control cards and configuration files. On the basis of how these source components are handled during rehosting to a target platform, there are two main ways via which application rehosting can be achieved. Retaining the Technology Stack This method makes sure that the change required in the existing technology stack of the application during rehosting is minimum, thereby eliminating risk to a high degree and greatly reducing the time taken for the migration. To achieve all this, it necessitates the presence of an Application Execution Environment (usually in the form of a software emulation layer) that provides behavior and technology support similar to the source mainframe. However, this method uses the target platform environment merely as a foundation for the emulation layer and doesn’t immediately exploit the features of the environment for the application. Usually, in this method of rehosting, the task of altering the technology stack is taken up as a follow-up/ phase-2 activity. Altering the Technology Stack This method ensures that the way the end-users interact with the application and application functionality remains unchanged but changes a few components in the technology stack to take advantage of the target platform environment. For example, JCLs are converted to Shell Scripts; BMS Maps are converted to .NET screens etc. However, the technology conversion makes this method inherently more risky and would require more effort and time spent on risk mitigation efforts when compared to the previous method. Proven emulation platforms, tools and techniques by multiple vendors are available for rehosting of either type. (Refer to Appendix-A for a comparison between some of the main players in this space). When to choose Rehosting All Legacy Applications are not automatically suited for rehosting. The choice of migration strategy depends on various factors like © 2011, HCL Technologies. Reproduction Prohibited. This document is protected under Copyright by the Author, all rights reserved.
  • 6. Virtual Mainframe - Legacy Application Rehosting | April 2011 the size, complexity and criticality of the applications and systems in consideration. For e.g., SMEs (Small and Medium Enterprises), could very well apply Rehosting as a Mainframe Replacement strategy, because all of their applications might fit cleanly into a non-mainframe platform. On the other hand, in case of Large Mainframe shops, rehosting of non-critical work off the mainframe can free up the MIPS for more critical data processing needs and also help defer their mainframe upgrade plans thereby benefitting from a hybrid Mainframe + Rehosting solution. They main factors that need to be considered are: Technology Factors Business Factors The availability of an Execution En- Organization’s technology roadmap vironment for the technology stack and business plans that the Legacy on the preferred target platform Application must cater to The proportion of the technology Business criticality of the stack that is not readily Rehostable Legacy Application and requires some change The availability of options to port or Current TCO of the mainframe replicate the existing eco-system and the potential reduction in cost on the preferred target platform (TCO) which can be achieved Size of the mainframe, in MIPS, The time period in which cost that is being targeted for migration reduction can be achieved (ROI) Table C: Factors influencing migration options As a thumb rule, ‘Rehosting’ can be a viable solution where • Legacy Application has a fairly standard mainframe technology stack (COBOL, PL/1, CICS, JCL, VSAM, GDG, DB2, IMS, BMS) • The mainframe MIPS consumption costs are disproportionately higher compared to associated business value which is derived from the mainframe • Quick turn-around is required for the migration Rehosting Benefits The benefits that Application Rehosting brings to the table can be categorized as below: Continuity It allows organizations to continue using the stable applications that they have relied upon for long, since it involves using the same application and technology stack but on a different platform. Extensive retraining of valuable personnel is eliminated and current skill sets can be reused. This minimizes disruptions to existing teams and workflows. Low Risk Since the amount of change required in the application is comparatively minimal or non-existent (as against COTS or Re-engineering), this exercise is ‘low risk’ by definition. © 2011, HCL Technologies. Reproduction Prohibited. This document is protected under Copyright by the Author, all rights reserved.
  • 7. Virtual Mainframe - Legacy Application Rehosting | April 2011 Low Cost The costs involved in procuring, operating and upgrading the target platform, in terms of hardware as well as software, are substantially lower when compared to the costs incurred for the equivalent components on the Mainframe. This results in huge cost savings for the organization post-Rehosting, with typical ROI within 18 to 24 months. It also significantly reduces cost of operations, freeing up the IT budget for full modernization and innovation. Less Effort ince most of the application technology stack is retained, existing development and maintenance resources can be reused with minimal retraining. It also ensures that end-users are not faced with any radically new way of interacting with the application, thereby reducing end-user re-training efforts. Scalability Rehosting to a modern target platform provides the organization with the ability to scale the system up or down based on their load and growth. But more importantly, it opens the possibility of horizontally scaling out their application servers into a ‘cluster’. Flexibility Because the applications are now running on modern platforms, they can often be easily wrapped in a powerful GUI as opposed to the traditional character-based UI. This also makes it easier and cheaper to extend the existing applications with a Web Services front-end than when they were running on the mainframe. Rehosting vs. Other types of Migration Rehosting is inherently different from other types of Migration because: • It involves moving the existing application to the target platform with minimal or no changes to the way it currently exists and behaves whereas other migration options involve changing the entire application architecture, technology stack and usability • It requires the availability of compilation and run-time support for mainframe application source and data on the target platform whereas other option involve using the native environments available on the target platform • It mainly addresses the high costs and inherent inflexibility of running Legacy Applications while reducing risks involved in moving to a cheaper platform whereas other migration options usually address the challenges related to application code quality and architecture also • It is largely tool driven and achieves the porting and execution of Legacy Applications on the new platform with a high degree of automation whereas other options are comparatively more manual-work intensive and time consuming © 2011, HCL Technologies. Reproduction Prohibited. This document is protected under Copyright by the Author, all rights reserved.
  • 8. Virtual Mainframe - Legacy Application Rehosting | April 2011 Rehosting – Reference Architecture UI Layer IMS Screens 3270 BMS Others Batch Layer (JES) JCL/ PROC/ other CL Job Scheduler (CA-7/-11 etc.) Third party Utilities IBM Utilities (IEBCOPY, (Sync SORT etc.) IEBGENER etc.) RACF, CA Top Secret, ACF2 etc. Data Layer Security Layer Indexed DB2/ IMS GDG Flat Files Files DB etc. Application Layer 4GL 3GL X Gen Pac Base Business Business Logic in Logic in CA Ideal Other COBOL PL/1 Assembler, REXX, DYL280, SAS etc. Transaction Layer CICS TS IMS DC Other z/OS, OS390, Bull etc. UI Layer 3270 IMS Screens BMS JSP HTML .NET Web Services Batch Layer (Emulated JES/ OS Layer etc.) Active Directory, OpenLDAP, Other LDAP based products JCL/ PROC/ shell Scripts/ Job Scheduler (Autosys, Perl .... BMC Control...) Equivalent 3rd party utilities Data Layer Security Layer Indexed RDBMS GDG Oracle, DB2 SQL Flat Files Files Server etc. Application Layer 4GL 3GL Business Business Converted to Logic in Logic in supported 3GL COBOL PL/1 Converted to equivalent in supported 3GL Transaction Layer Emulated CICS/ IMS DC/ OLTP environments Windows, UNIX, Linux Figure 1 - Generic Rehosting Reference Architecture © 2011, HCL Technologies. Reproduction Prohibited. This document is protected under Copyright by the Author, all rights reserved.
  • 9. Virtual Mainframe - Legacy Application Rehosting | April 2011 Application Rehosting Process Legacy applications usually exist within an ecosystem of interfaces, tools and utilities on the mainframe which they actively interact with. Legacy applications, in general, also do not exist on the mainframe in isolation and as such share certain application assets and the mainframe resources with other applications. The presence of such interactions and dependencies makes it imperative that any rehosting exercise focuses on not just the application inventory but also on providing a similar eco-system on the target platform for the application to run in. In order to achieve that, the process of Rehosting should usually be as indicated: General Assessment Inventory Assessment Rehosting Strategy Platform Setup Pilot Rehosting Complete Rehosting Testing UAT Go-Live Figure 2 – Rehosting Process General Assessment This is the beginning of the process where the existing application on the mainframe is assessed to understand the following: Technology stack This includes identifying programming languages, scripting languages, transaction processing environments, batch and online technologies, files types, data types, database types and utilities. Application Environment This includes identifying processes for backups, archiving and DR, identifying application interfaces, character sets, compiler options, identifying batch scheduling, security and access management requirements and identifying utilities and third party tools being used. Usage and Performance This includes identifying application usage patterns, application load characteristics, application response times and base lining the performance of the application in its current state. © 2011, HCL Technologies. Reproduction Prohibited. This document is protected under Copyright by the Author, all rights reserved.
  • 10. 10 Virtual Mainframe - Legacy Application Rehosting | April 2011 Non-Performance Parameters This includes identifying the requirements – existing as well as future – for application availability, scalability, modification and extensibility. Inventory Assessment The general assessment is followed by a detailed inventory assessment. This is required in order to obtain: Size of application In terms of number of components and complexity of components. Technology Grouping Grouping of the components in terms of their technology to understand the size and proportion of each technology in the over-all technology stack. Rehosting Strategy The results of the assessment enables the formation of the rehosting strategy which consists of: • Choice of rehosting environment vendor • Strategy to handle un-supported technologies • Environment mapping • Target Architecture, Sizing and Workflow Rehosting Environment Setup This is where the target platform is built for the first time and configured as per the decided architecture. Pilot Rehosting As the saying goes, “The proof is in the pudding”. Having done the assessment and developed a strategy for the rehosting based on that definitely makes the exercise proceed smoothly and quickly but doesn’t provide a 100% guarantee that the strategy will succeed completely in meeting all the requirements. In order to save time, effort and costs, it is advisable to put the rehosting strategy to test by means of a Test run or Pilot done on a small, representative subset of the application. This will help identify any shortfalls in the overall rehosting strategy which can then be rectified accordingly. Rehost the complete application Once the strategy has been tested and perfected via the Pilot, the entire application – programs, scripts, screens, data, tools and utilities – can then be rehosted to the target platform in a smooth and efficient manner. Post-Rehosting Testing By definition, rehosting provides the same functionality of the legacy application on the target platform. Hence the focus of the © 2011, HCL Technologies. Reproduction Prohibited. This document is protected under Copyright by the Author, all rights reserved.
  • 11. 11 Virtual Mainframe - Legacy Application Rehosting | April 2011 testing effort in a typical rehosting exercise would be around the non-functional aspects like performance, stability and availability. Functional regression testing will also be carried out. UAT/ Parallel Run/ Field Testing In this phase, the target platform will be configured in the same way as it would eventually be as a live system and will be run alongside the mainframe. As much as possible, the same data will be used on both the platforms and end-users would be invited to use the rehosted platform. Using the new platform in a production like environment helps identify any final wrinkles in the rehosting strategy and eliminate them. Go-live The final phase, where the new target platform takes the place of the mainframe as the application platform. Training As a parallel activity which can be taken up along with any of the testing phases, training activities have to be started for the various teams that would be using the new platform. This includes: Application team They have to be trained in working with new IDEs which will be used for ongoing application development and maintenance activities. Administration team They have to be trained in the administration of the various components that make up the new application ecosystem. Decommissioning Modernization Once the new platform is in place, plans for decommissioning the application from the mainframe as well as for modernizing and extending the rehosted application can be worked on. End Notes One size doesn’t fit all in the context of legacy modernization. There is no single, pre-packaged solution that is right for everyone seeking to modernize their existing mainframe applications. While the traditional legacy modernization and migration methods have their place, “Legacy Rehosting” makes a strong case for itself as a viable modernization solution because of the benefits it provides in terms of reduced migration risk, short implementation time frame, faster ROI and greatly reduced TCO. “Legacy Rehosting” works for enterprises irrespective of their mainframe footprint. It can be leveraged either to completely replace their mainframes or for partial workload offloading from the mainframe. In either case the end result is a sizable reduction in their overall mainframe costs. © 2011, HCL Technologies. Reproduction Prohibited. This document is protected under Copyright by the Author, all rights reserved.
  • 12. 12 Virtual Mainframe - Legacy Application Rehosting | April 2011 Appendix – A TP BP Other engines Appli‑ tools Data Platform Runtime cation (Monitor‑ Support environ‑ handling ing, Secu‑ ment rity etc.) Microfo‑ Windows Server Minimal ISAM Via 3rd cus UNIX Enterprise to No GDG Party Linux Edition (for change Any TPE BPE) RDBMS MFCOBOL Runtime Clerity Windows UniKix TPE Minimal ISAM Provides UNIX UniKix BPE to No Oracle, Monitoring, Linux change DB2 UDB Security vCOBOL and Access Runtime mgmt. All others via 3rd Party Oracle UNIX Tuxedo as JCL ISAM Via 3rd Tuxedo Linux TPE converted Oracle, Party OS Shell as to shell DB2 UDB BPE scripts MFCOBOL BMS or Net- converted COBOL to JSP/ HTML Fujitsu Windows NeoKicks BMS Convert Via 3rd Alchemy and .NET converted indexed Party NeoBatch to ASP. file to NET tables NetCOBOL Runtime Any RDBMS COBOL- Windows XCICS JCL VSAM Provides IT UNIX XeBE converted Emulation Schedul- HTWC Linux to shell Any ing. All COBOL-IT scripts RDBMS others via or Net- 3rd Party COBOL TMax‑ UNIX Open- Minimal VSAM Via 3rd Soft Linux FRAME (for to No Emulation Party TPE and change Any BPE) RDBMS Own COBOL Runtime IBM TX- Windows TX-Series JCL VSAM Via 3rd Series UNIX (CICS) as converted Emulation Party Linux TPE to shell Any No JCL scripts RDBMS support MFCOBOL or Net- COBOL ***Click on the vendor name for the website © 2011, HCL Technologies. Reproduction Prohibited. This document is protected under Copyright by the Author, all rights reserved.
  • 13. 13 Virtual Mainframe - Legacy Application Rehosting | April 2011 References 1. Wikipedia http://en.wikipedia.org/wiki/History_of_IBM_mainframe_ operating_systems 2. The History of Computing Project http://www.thocp.net/hardware/mainframe.htm 3. IBM http://www-03.ibm.com/ibm/history/exhibits/mainframe/ mainframe_intro.html 4. University of Maryland, Baltimore County http://www.cs.umbc.edu/courses/graduate/631/Fall2002/ COBOL.pdf 5. Microsoft http://www.microsoft.com/downloads/en/details. aspx?FamilyID=1637d24d-fb67-4d6e-adc7-e101981c728bdispla ylang=en About the Authors Santosh Kumar is a Mainframe migration/modernization architect with the HCL Mainframe Solutions Centre of Excellence. He has around 10 years of Mainframe development and solutions experience and has been involved in architecting multiple large scale legacy modernization programs. Vishnu Prasad is a Senior Project Manager handling Legacy Application Rehosting with the HCL Mainframe Solutions Centre of Excellence. He has around 10 years of Mainframe development and modernization solutions design experience. © 2011, HCL Technologies. Reproduction Prohibited. This document is protected under Copyright by the Author, all rights reserved.
  • 14. 14 Virtual Mainframe - Legacy Application Rehosting | April 2011 About HCL HCL Technologies HCL Technologies is a leading global IT services company, working with clients in the areas that impact and redefine the core of their businesses. Since its inception into the global landscape after its IPO in 1999, HCL focuses on ‘transformational outsourcing’, underlined by innovation and value creation, and offers integrated portfolio of services including software-led IT solutions, remote infrastructure management, engineering and RD services and BPO. HCL leverages its extensive global offshore infrastructure and network of offices in 26 countries to provide holistic, multi-service delivery in key industry verticals including Financial Services, Manufacturing, Consumer Services, Public Services and Healthcare. HCL takes pride in its philosophy of ‘Employee First’ which empowers our 72,267 transformers to create a real value for the customers. HCL Technologies, along with its subsidiaries, had consolidated revenues of US$ 3.1 billion (Rs. 14,101 crores), as on 31st December 2010 (on LTMbasis). About HCL Enterprise HCL is a $5.5 billion leading global technology and IT enterprise comprising two companies listed in India - HCL Technologies and HCL Infosystems. Founded in 1976, HCL is one of India’s original IT garage start-ups. A pioneer of modern computing, HCL is a global transformational enterprise today. Its range of offerings includes product engineering, custom package applications, BPO, IT infrastructure services, IT hardware, systems integration, and distribution of information and communications technology (ICT) products across a wide range of focused industry verticals. The HCL team consists of over 79,000 professionals of diverse nationalities, who operate from 31 countries including over 500 points of presence in India. HCL has partnerships with several leading Global 1000 firms, including leading IT and technology firms. For more information, please visit www.hcl.com. © 2011, HCL Technologies. Reproduction Prohibited. This document is protected under Copyright by the Author, all rights reserved.