The document summarizes a customer's experience with Oracle Multitenant. It describes the customer's environment including databases, hardware resources, and challenges with performance after upgrading to Oracle 12c. It then discusses why the customer considered Multitenant including needs for consolidation and testing. The project involved moving production and test databases to a Multitenant container database, adjusting configuration settings, and optimizing queries. The results were improved performance and ability to scale resources. New features in Oracle 12.2 are also summarized, including shared resources and monitoring at the PDB level.
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Constomer Context
The name will not be disclosed but the most relevant
characteristics to the project are reported below.
Customer
Environment
Medium size customer from financial sector
Few databases with different workload types
Virtual Private Databases
High level of automation
Consolidation opportunities with the Multitenant Option
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Backgrounds
2013 : Initial setup
Oracle 11.2.0.3
dNFS
6 Cores per nodes
2 Production RAC databases
DataGuard
4 Cores per nodes
2 Standby RAC databases ADG
Up to 5 test databases
ODA V1
• 96 GB of RAM per nodes
• 24 cores (12 per nodes)
• 6 TB in Normal Redundancy
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Backgrounds
2015 : Upgrade
Oracle 12.1.0.2 with Singletenant
6 Cores per nodes
2 Production RAC databases
4 Cores per nodes
2 Standby RAC databases ADG
Up to 5 test databases
ODA V1
• 96 GB of RAM per nodes
• 24 cores (12 per nodes)
• 6 TB in Normal Redundancy
dNFS
DataGuard
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Backgrounds
Performance challenges after migration to 12c
Execution plan changes
Data model
Stale statistics
Some queries with huge performance deviations
New 12c features
• SQL Plan directives due to miss estimates
• Adaptive dynamic sampling triggered automatically when parallelism is
in the game
• Some bugs…
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Why considering Multitenant
New customer to absorb
Double the size of all databases
Have the same performance in test environments
Same automation procedures
Keep eyes to the cost!
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Why considering Multitenant
2016 : Second Upgrade
Oracle 12.1.0.2 with Multitenant
6 Cores per nodes
2 Production RAC databases
DataGuard
6 Cores per nodes
2 Standby RAC databases ADG
Up to 5 test databases
ODA X5-V2
• 256 GB of RAM per nodes
• 72 cores (36 per nodes)
• 64 TB in Normal Redundancy
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Project execution
Production databases
One small OLTP database
One mix OLTP-DWH medium database
VPD!
Financial consolidation can be scheduled at any time by end
users
Average execution time is within one hour
Parallel executions are used for certain steps
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Project execution
Test databases
Can be refreshed on demand
Directly from production
From any backup
Performance tests before pushing changes into production
Has to be closest to production in term of resource allocation
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Project execution
What have we done?
Use more SGA as the ODA X5-2 (256 GB per nodes versus 96 GB)
Remove instance caging and introduce a CDB Resource Plan
Limit the PGA by setting pga_aggregate_limit parameter
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Project execution
Adjust statistics collection methods
Relocate some tablespaces
Optimize Undo for temporary tables by setting
TEMP_UNDO_ENABLED parameter
Setup Result Cache for some queries
Fine tune some queries
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Project execution
Result after few days
Customer was happy, jobs are running 55% faster
Refreshes from production are completed 40% faster
Performance in test environment is becoming comparable to
production
General end user perception was good!
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Project execution
Quiz 1
Production Instance was very slow
Several jobs were running into the two PDBs
Massive database waits: free buffer waits!!
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Project execution
Possible causes:
The I/O system is slow.
Waiting for resources, such latches.
The buffer cache is so small and DBWR spends most of it's
time cleaning out buffers for server processes.
The buffer cache is so big and they are not enough DBWR
processes to free enough buffers in the cache to satisfy
requests.
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Project execution
Quiz 2
Production Instance was very slow
Many small transactions were running into one PDB
Massive database waits: latch free!!
Result_cache latch
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Project execution
Possible causes:
Some tables have the result_cache property to force.
To many queries with Result_Cache hint.
To many concurrent sql plan directives running.
There is not enough shared pool to handle all
result_cache requests.
The result_cache_mode parameter was set to FORCE
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Project execution
Limitations of the 12.1 version
Cannot clone a PDB online
Cannot flashback or point in time at PDB level
SGA per PDB
IO management per PDB
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Conclusion
Multitenant is becoming and will be a key player
It’s just consolidation topic that you have to address
trivadis is your key helper!
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trivadis Oracle Multitenant Workshop
This workshop will give you a complete and comprehensive overview to manage and
take profit of the Multitenant option.
Content
Concepts and Architecture Overview
What is Consolidation
About provisioning and cloning
Manage your resources efficiently
Patching in Multitenant Environment
Language
French
English
Organization
2 days
Theory - Mornings
Practice - Afternoons
Participants: Minimum 1, Maximum 6
Materials
You will be given Workshop PDF, two virtual
machines under Linux and scripts of exercises
covering all topics.