1. 1
Designing and Developing your
Database for Application Availability
Presented to the Melbourne CBD SQL PASS Chapter.
Saxons - Level 8, 500 Collins Street. Melbourne, Australia
12:30 – 14:00, July 26th 2010
Charley Hanania, QS2 AG
B.Sc (Computing), MCP, MCDBA, MCITP, MCTS, MCT, Microsoft MVP: SQL Server
Senior Database Specialist

2. My Background
• Now:
• Microsoft MVP: SQL Server
• Database Consultant (again, and very happy) at QS2 AG
• Formerly:
• Production Product Owner of MS SQL Server Platform at UBS Investment Bank
• Technical Team Lead
• ITIL v3 Certified
• SQL Server Certified since 1998
• On SQL Server since 1995
• Version 4 on OS/2
• IT Professional since 1992
• PASS
• Chapter Leader – Switzerland
• Regional Mentor – Europe
• European PASS Conference Lead
• Event Speaker
2
26 July, 2010
Designing
&
Developing
Databases
for
Application
Availability

3. Contact Info
• Email: Charley.Hanania@sqlpass.org
• Website: http://www.sqlpass.ch <- Slides here
• Twitter: http://www.twitter.com/CharleyHanania
• Blog: http://blogs.mssqltips.com/blogs/charleyhanania
• Linked-in: http://www.linkedin.com/in/charleyhanania
3
26 July, 2010
Designing
&
Developing
Databases
for
Application
Availability

4. Agenda
• General Barriers to Application Availability
• Standard High Availability Methodology
• General Standard - Clustering
• One up on the Standard – Database Mirroring
• Decreasing component start-up time
• Instant File Initialisation
• Partitioning your Database Infrastructure
• Eureka! Partitioning for Availability (PfA)
• Basic PfA Methodology
• Code Samples
• Questions
Designing
&
Developing
Databases
for
Application
Availability
4
26 July, 2010

5. General Barriers to Availability
Designing
&
Developing
Databases
for
Application
Availability
6
26 July, 2010
Simplistic Network Topology View:
Slightly more realistic view:
And that’s just scratching the surface of the Peripherals!
Think about the layered complexity of the supporting software and drivers…!
Environmental Complexity

6. Standard HA Methodology
• Keep it up for as long as possible.
• Increase redundancy
• Decrease Single Points of Failure
• Bring it back as quickly as possible
• Decrease the dependency sequence
• Decrease component start-up time
Designing
&
Developing
Databases
for
Application
Availability
7
26 July, 2010

7. General Standard - Clustering
• Keep it up for as long as possible.
• Increase redundancy
• Additional Servers waiting in readiness 
• Increased redundancy = increased cost 
• Increased redundancy = decreased
utilisation 
• Decrease Single Points of Failure
• Virtual IP Addresses 
• Virtual Network Names 
• Additional Network Cards etc 
• Storage 
• Bring it back as quickly as possible
• Decrease the dependency
sequence
• Server is Started 
• SQL Instance is an exclusive Cluster
Resource 
• Decrease component start-up time
• Instant File Initialisation 
• App Database isn’t useable until Primary
Data File is opened and recovered 
26 July, 2010
Designing
&
Developing
Databases
for
Application
Availability
8
Primary
Standby

8. Database Mirroring
• We could discuss the architecture, benefits and uses of DB
Mirroring, but I’m told you’re mainly architects and
developers, and the doors here aren’t locked…
• If you’d like to discuss DB Mirroring, we can chat after the
session…
Designing
&
Developing
Databases
for
Application
Availability
9
26 July, 2010

9. Decreasing Component Startup Time
(Another DBA point, but one that is Golden and not to be missed!)
• Data and log files are first initialized by being filled and with
zeros when created or restored.
• When SQL Server Starts, the tempdb database is recreated.
• Application databases do not come online until tempdb has.
• If large, then startup times can be quite long!
• Action:
• Ensure that instant file initialisation is set (Windows:
SE_MANAGE_VOLUME_NAME right)
• The group that the SQL Server Service Account is in needs to be
added to the Perform Volume Maintenance Tasks security policy,
in the “Local Security Policy” Tool.
• I’ve seen this reduce SQL Server Startup from 8 minutes to 1
second (max)
Designing
&
Developing
Databases
for
Application
Availability
10
26 July, 2010
INSTANT FILE INITIALISATION

10. Decreasing Component Startup Time
• Msdn lists the following (summarised)
• Hardware Partitioning
• Multiprocessors that enable multiple threads of operations.
• RAID (redundant array of independent disks) devices
• A table striped across multiple drives can typically be scanned faster than
the same table stored on a single drive.
• Horizontal Partitioning
• Divide tables into multiple tables containing the same number of
columns, but fewer rows.
• Partitioning data horizontally based on age and use is common.
• Vertical Partitioning
• Divide tables into multiple tables containing fewer columns through
normalization and row splitting.
Designing
&
Developing
Databases
for
Application
Availability
11
26 July, 2010
PARTITIONING DATABASE COMPONENTS

11. Additional Partitioning Options
• Logical Schema Partitioning
• Used mainly for securing and grouping objects by department,
role, application etc…
• Physical Partitioning
• Of Files and Filegroups
• Used mainly for performance
• Files placed on multiple different data volumes
• Multiple files created for round-robin writes and extent allocations
Designing
&
Developing
Databases
for
Application
Availability
12
26 July, 2010

12. Eureka! Partitioning for Availability
• Each database has an area similar to a disk’s boot record
• For a database this resides in the Primary data file
• If this file is corrupt or unavailable, the database will not be
loaded and opened regardless of other data files
• A good practice is to not put any objects in this data file, and to
put all your tables and objects into secondary data files.
• Within the DB you can distribute objects into files to achieve
one or more of the following
• Enable an application to continue working when other data files
are missing or corrupt by grouping needed objects together
• Restore the most critical files for your application system to start
up first, allowing partial functionality of your application to
continue without issue.
Designing
&
Developing
Databases
for
Application
Availability
13
26 July, 2010

13. 14
Designing
&
Developing
Databases
for
Application
Availability
26 July, 2010
Open Discussion
Which ways could we split the adventureworks db,
focussed on client facing / downstream application
functionality, criticality and startup sequence for
Availability?

14. Adventureworks Schema

15. PfA Methodology
• Conceptual extension from Logical Schema Partitioning and
Physical File Partitioning:
1. Don’t put user defined objects in the Primary FileGroup
i. Allows the Primary Filegroup to load faster
2. Schema Separate user defined objects
i. For clarity of purpose and operational use
ii. Try not to use dbo schema (good design/operational practice)
iii. DBA’s will schematize objects in a similar fashion to what was in the
Adventureworks sample. For PfA you should look to map your schema’s
around your application’s core functionality and use cases and criticality
3. Create Filegroups for each Schema
i. Multiple if you want to partition historical data horizontally etc
ii. Name them in a fashion that allows easy understanding of what is
in them, or how they should be used.
Designing
&
Developing
Databases
for
Application
Availability
16
26 July, 2010

16. PfA Methodology(2)
• Conceptual extension from Logical Schema Partitioning and
Physical File Partitioning:
4. Design your application to modularise its data access needs
i. This is critical to segmenting your application to specific data
files/filegroups.
ii. This includes stored procedure and function internals, use
try/catch within sp’s for example to decide whether rollback or
other functionality is needed when a filegroup is offline.
iii. The key flows could be
 to either contain data access within the necessary filegroups, or
 determine whether a function can be used to catch that an object is in an
offline filegroup and skip it / do something else / roll back, or
 Catch “Msg 8653, Level 16, State 1, Line 3”* and do as per point above.
5. Document application’s modules, with emphasis on criticality
and data dependencies.
i. Allows stepped sequencing of apps by criticality during start up
Designing
&
Developing
Databases
for
Application
Availability
17
26 July, 2010
*[Tambs] While the database is in a state of partial availability, the filegroups that
remain online can support queries. However, queries that depend on data that
resides in filegroups that are offline return error 8653:
Msg 8653, Level 16, State 1, Line 3
The query processor is unable to produce a plan for the table or view 'X' because
the table resides in a filegroup which is not online.

17. 18
Designing
&
Developing
Databases
for
Application
Availability
26 July, 2010
Adding Files and File Groups to a Database
USE [master]
GO
CREATE DATABASE [PfA]
ON PRIMARY
(
NAME = N'PfA_Primary'
,FILENAME = N'E:MSSQL10.SQL2008INST01MSSQLDataPfA_Primary.mdf'
,SIZE = 400MB
),
FILEGROUP [PfA_FG1]
(
NAME = N'PfA_F1_FG1'
,FILENAME = N'E:MSSQL10.SQL2008INST01MSSQLDataPfA_F1_FG1.ndf'
,SIZE = 300MB
),
(
NAME = N'PfA_F2_FG1'
,FILENAME = N'E:MSSQL10.SQL2008INST01MSSQLDataPfA_F2_FG1.ndf'
,SIZE = 300MB
),
FILEGROUP [PfA_FG2]
(
NAME = N'PfA_F1_FG2'
,FILENAME = N'E:MSSQL10.SQL2008INST01MSSQLDataPfA_F1_FG2.ndf'
,SIZE = 300MB
),
FILEGROUP [PfA_FG3]
(
NAME = N'PfA_F1_FG3'
,FILENAME = N'E:MSSQL10.SQL2008INST01MSSQLDataPfA_F1_FG3.ndf'
,SIZE = 300MB
)
LOG ON
(
NAME = N'PfA_log'
,FILENAME = N'F:MSSQL10.SQL2008INST01MSSQLLogsPfA_PfA_log.LDF'
,SIZE = 100MB
)
GO
USE [PfA];
GO
SELECT * FROM sys.database_files;
SELECT * FROM sys.filegroups;

18. 19
Designing
&
Developing
Databases
for
Application
Availability
26 July, 2010
Create and Allocate Objectsto Schemas
USE [PfA];
GO
CREATE SCHEMA [Sales];
GO
CREATE SCHEMA [Production];
GO
CREATE SCHEMA [Person];
GO
-- moving tables from dbo schema to
-- [Production] and [Sales] schemas
ALTER SCHEMA [Sales]
TRANSFER [dbo].[Customer];
-- Note that triggers move as well...
GO
ALTER SCHEMA [Production]
TRANSFER [dbo].[BillOfMaterials];
GO
ALTER SCHEMA [Person]
TRANSFER [dbo].[ContactInsert];
GO
ALTER SCHEMA [Person]
TRANSFER [dbo].[Contact];
GO
-- change stored proc definitions to focus on right schemas
ALTER PROC [dbo].[ContactInsert]
(
@VbiContactID BIGINT
,@VvcSalutation VARCHAR(4) = NULL
,@VnvcForename NVARCHAR(100),@VnvcMiddlename NVARCHAR(100) = NULL
,@VnvcSurname NVARCHAR(100),@VvcJobTitle NVARCHAR(100) = NULL
,@VvcCompany NVARCHAR(100) = NULL,@VnvcAddressLine1 NVARCHAR(100)
,@VnvcAddressLine2 NVARCHAR(100) = NULL
,@VnvcAddressLine3 NVARCHAR(100) = NULL
,@VvcPostCode VARCHAR(12),@VnvcCity NVARCHAR(50)
,@VnvcState NVARCHAR(50) = NULL,@VinCountryID INT
,@VvcEmailAddress VARCHAR(100),@VvcBusinessPhone VARCHAR(25)
,@VvcBusExt VARCHAR(10) = NULL,@VvcFacsimile VARCHAR(25) = NULL
,@VvcMobilePhone VARCHAR(25) = NULL,@VvcPassword VARCHAR(20)
)
AS
INSERT INTO [Person].[Contact]
([ContactID],[Salutation]
,[Forename],[Middlename]
,[Surname],[JobTitle]
,[Company],[AddressLine1]
,[AddressLine2],[AddressLine3]
,[PostCode],[City]
,[State],[CountryID]
,[EmailAddress],[BusinessPhone]
,[BusExt],[Facsimile]
,[MobilePhone],[Password])
VALUES
(@VbiContactID,@VvcSalutation
,@VnvcForename,@VnvcMiddlename
,@VnvcSurname,@VvcJobTitle
,@VvcCompany,@VnvcAddressLine1
,@VnvcAddressLine2,@VnvcAddressLine3
,@VvcPostCode,@VnvcCity
,@VnvcState,@VinCountryID
,@VvcEmailAddress,@VvcBusinessPhone
,@VvcBusExt,@VvcFacsimile
,@VvcMobilePhone,@VvcPassword);
GO
* Use Synonyms to help the transition from
dbo native schema to proper schema usage

19. 20
Designing
&
Developing
Databases
for
Application
Availability
26 July, 2010
Allocate an Object to a Filegroup
CREATE TABLE [Sales].[SalesInvoice]
(
[SalesInvoiceID] INT IDENTITY(1,1) PRIMARY KEY CLUSTERED
,[Amount] MONEY
,[CustomerID] INT
,[DateInvoiced] DATETIME
,[DatePaid] DATETIME
) ON [PfA_FG1];
GO
• Creating tables on a filegroup is easy as per the code sample.
• Moving existing tables can be a little more complicated:
• Use Create index (clustered) with Drop Existing
• Rebuild indexes etc to move them
• It may take many iterations to get the sequencing and code here
right, but its worth it in the long run.

20. 21
Designing
&
Developing
Databases
for
Application
Availability
26 July, 2010
Retry Logic (1)
ADO.NET Code Example (http://technet.microsoft.com/en-us/library/cc917713.aspx#ECAA)
This code example uses ADO.NET 2.0 (SqlClient). The following parameters are used in the example.
strConn is the database connection string that includes the failover partner.
strCmd is the command, such as Transact-SQL or a stored procedure, to execute.
iRetryInterval is the number of seconds to wait (sleep) between retries.
iMaxRetries is the number of times to retry the command before failing.
Example connection string ( strConn )
Data Source=SQLAINST1;Failover Partner=SQLBINST1;
Initial Catalog=DBMTest;Integrated Security=True
using System.Data;
using System.Data.SqlClient;
using System.Threading;
bool ExecuteSQLWithRetry_NoResults(string strConn,
string strCmd,
int iRetryInterval,
int iMaxRetries)
{
// Step 1: Enter the retry loop in case an error occurs
for (int iRetryCount = 0; iRetryCount < iMaxRetries; iRetryCount++)
{
try
{
// Step 2: Open the database connection
conn = new SqlConnection(strConn);
conn.Open();
// Step 3: Execute the command
if (null != conn && ConnectionState.Open == conn.State)
{
cmd = new SqlCommand(strCmd, conn);
cmd.ExecuteNonQuery();
// Step 4: If there were no errors, clean-up & return success
return true;
}
}
catch (Exception ex)
{
// Step 5: Catch Error on Open Connection or Execute Command
// Error Handling to be added here: ex
}
• I expect that the code here will only need
slight Adjustments for use with Clustering
• Connection string would use virtual name
• Timeout retry delay would cater for longer
startup/failover

21. 22
Designing
&
Developing
Databases
for
Application
Availability
26 July, 2010
Retry Logic (2)
finally
{ // Step 6: Clean up the Command and database Connection objects
try
{
// Clean Command object
if (null != cmd)
cmd.Dispose();
cmd = null;
// Clean up Connection object
if (null != conn && ConnectionState.Closed != conn.State)
conn.Close();
conn = null;
}
catch (Exception ex)
{
// Error handling to be added here
}
}
// Step 7: If the maximum number of retries not exceeded
if (iRetryCount < iMaxRetries)
{
// Step 7a: Sleep and continue (convert to milliseconds)
Thread.Sleep(iRetryInterval * 1000);
}
} // end for loop: iRetryCount < iMaxRetries
// Step 7b: If the max number of retries exceeded, return failure
return false;
}
Continued…

22. 23
Designing
&
Developing
Databases
for
Application
Availability
26 July, 2010
Query Returning Files, Filegroups and Sizes
SELECT
s.data_space_id as Id
,g.name as Filegroup_name
,s.name as Logical_name
,physical_name
,g.is_default AS [IsDefault]
,g.is_read_only AS [ReadOnly]
,CAST(
ISNULL
(
(
SELECT
SUM(gs.size)*CONVERT(float,8)
FROM
sys.database_files gs
WHERE
gs.data_space_id = g.data_space_id
), 0
) AS float
) AS [Size]
FROM
sys.filegroups AS g
INNER JOIN
sys.master_files AS s
ON (s.data_space_id = g.data_space_id)
WHERE
s.type = 0
AND
s.database_id = db_id()
AND
s.drop_lsn IS NULL; From “Partial Database Availability”
(Danny Tambs, May 2007)

23. Links and Resources
• AdventureWorks Database Diagram
• http://www.microsoft.com/downloads/details.aspx?FamilyID=0f6e0bcf-a1b5-4760-8d79-
67970f93d5ff&DisplayLang=en
• Whitepaper: “Partial Database Availability” (Danny Tambs, May 2007)
• http://technet.microsoft.com
• Whitepaper: “Partitioned Table and Index Strategies Using SQL Server 2008” (Ron
Talmage, March 2009)
• http://technet.microsoft.com
Designing
&
Developing
Databases
for
Application
Availability
24
26 July, 2010

24. Questions?
Designing
&
Developing
Databases
for
Application
Availability
25
26 July, 2010