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Tips for Upgrading to Oracle 11g

Oracle Tips by Burleson Consulting

Many people ask what they should upgrade when they undertake a migration to Oracle 11g.  Oracle does not run in a vacuum, and Oracle 11g is heavily dependent on the environment, the operating system as well as the applications layer.

Remember, migrations are always risky, and even the most rigorous testing cannot always guarantee that you won’t experience an unplanned outage in production.  It’s always a good idea to do only one thing at a time, and when migrating to a new database release, it’s a best practice to follow a “bottom up” approach, upgrading at the lowest level first:

1.   Operating system upgrade:  We start by migrating the underlying OS to a current release.

 

2.   Oracle Upgrade:  Upgrade Oracle to 11g.

 

3.   Language upgrade: Once the database is stabilized, you can now look at upgrading your procedural languages (C++, Java, etc.).

 

4.   Applications Upgrades:  After the DBMS has been upgraded, you can look at upgrading the Application Server and ancillary application software.

 

5.   New Features:  Once the 11g system is stabilized in production, you can then explore implementing new database features.

For example, consider a shop using Oracle Enterprise Business Suite (EBS).  Oracle Applications is a huge product, and planning a full upgrade can involve hundreds of steps and take many months of careful planning.

When upgrading Oracle you may also want to consider upgrading your application server software.  Normally this is based on the certification matrix from your vendor, and there can be a lag from 6 months to several years before a vendor application package is certified for the newest release of Oracle.  

Remember, it is very risky to implement simultaneous changes.  Even a low level change like an upgrade to UNIX can cause issues with the end-user application, and you should always do a bottom-up approach. 

For Oracle systems, you start by reviewing the certification matrix for Oracle 11g and upgrade to the latest stable release of your operating system.  A few caveats for OS upgrades include getting the getting the 2nd release:  Nobody wants to be the first to encounter bugs, and savvy shops will always wait for the second major version to upgrade.  Most shops will upgrade from 10g release 2 to Oracle 11g release 2, and wait until the second major release of the OS environment.

It is a best practice to start with the OS upgrade, then the database software, then to application server software, followed last by the application software.

Generally, shops will want for a full business cycle (weekly or monthly) before moving up to the next layer, upgrading the OS and running for a month, upgrading Oracle and running for a month, upgrading the app server and tuning for a month, and finally upgrading the application software and running for a month.

Oracle 11g has many new features, many of which are in-line with the trends in the IT industry, recognizing that hardware changes rapidly over time.  Many shops are upgrading their hardware and software along these industry trends:

·         Monolithic server:  There is a massive trend toward Oracle instance consolidation as shops abandon the archaic one-server/one-instance architecture in favor of the new giant servers that can manage dozens of Oracle instances.

·         More CPU:  Oracle 11g has improvements to parallel query and many shops are considering adding processes to their servers to speed-up full-scan operations.

·         Solid-state disks:  Oracle now has the flash cache working for Linux, and with the Sun acquisition, it’s a sure bet that Oracle will be offering a super fast solid-state release of Oracle in the near future.

·         Virtualization:  Using VMware for Oracle goes along with server consolidation as noted in the book Oracle on VMware.  While virtualization is a hot topic right now, the very best way to share computing resources is to do nothing at all, and there are existing methods for adding CPU “governors” with CPU caging to keep any one instance from hogging too much CPU.  Of course, the DBA decides how much shared RAM each instance gets, so this is not an issue.

·         Compression – Oracle 11g compression is one of the hottest new features because it’s transparent and effective.  While compression does indeed make tables smaller, the real benefit of Oracle 11g compression ifs the ability to perform faster range-scan and full-scan operations because more data is fetched with each I/O operation.

Oracle 11g Software upgrades

Industry trends aside, Oracle has hundreds of new features to choose from and you need to be able to separate the wheat from the chaff.  For an excellent treatment of 11g new features from a functional perspective, I recommend the book Oracle 11g New Features by John Garmany, V. J. Jain, with Oracle ACE’s Lutz Hartmann, Brian Karr and Stave Karam.

Oracle 11g has many new DBA new features to make it easier to manage complex databases:

·         Enhanced ILM - Information Lifecycle Management (ILM) has been around for decades, but Oracle has made a push to codify the approach in 11g. 

·         Table-level control of CBO statistics refresh threshold - When Oracle automatically enables statistics collection, the default "staleness" threshold of 10% can now be changed with the dbms_stats.set_table_prefs procedure:

 

·         File Group Repository - Oracle introduced an exciting new feature in 10gr2 dubbed the Oracle File Group Repository (FGR).  The FGR allows the DBA to define a logically-related group of files and build a version control infrastructure.  

  •  Interval partitioning for tables - This is a new 11g partitioning scheme that    automatically creates time-based partitions as new data is added.

·         Server-side connection pooling - In 11g server-side connection pooling, an additional layer to the shared server, to enable faster [actually to bypass] session creation.

 

·         Capture/replay database workloads - Sounds appealing. You can capture the workload in prod and apply it in development. Oracle is moving toward more workload-based optimization, adjusting SQL execution plans based on existing server-side stress. 

 

·         Data Guard - Standby snapshot - The new standby snapshot feature allows you to encapsulate a snapshot for regression testing.  You can collect a standby snapshot and move it into your QA database, ensuring that your regression test uses real production data.

 

·         Quick Fault Resolution - Automatic capture of diagnostics (dumps) for a fault.

Oracle is big on automation and we see these new 11g automation features:

·         Automated Storage Load balancing - Oracle’s Automatic Storage Management (ASM) now enables a single storage pool to be shared by multiple databases for optimal load balancing. Shared disk storage resources can alternatively be assigned to individual databases and easily moved from one database to another as processing requirements change.

·         Automatic Diagnostic Repository - When critical errors are detected, Oracle automatically creates an “incident” ticket, notifying the DBA instantly.

·         Automatic Diagnostic Repository (ADR) - When critical errors are detected, they automatically create an “incident”. Information relating to the incident is automatically captured, the DBA is notified and certain health checks are run automatically.

11g RAC new Features

Oracle continues to enhance Real Application Clusters in Oracle11g and we see some exciting new features in RAC manageability and enhanced performance:

·         Oracle 11g RAC parallel upgrades - Oracle 11g promises to have a rolling upgrade features whereby RAC database can be upgraded without any downtime. 

·         Oracle RAC load balancing advisor - Starting in 10gr2 we see a RAC load balancing advisor utility.  Oracle says that the 11g RAC load balancing advisor is only available with clients which use .NET, ODBC, or the Oracle Call Interface (OCI).

·         ADDM for RAC - Oracle will incorporate RAC into the automatic database diagnostic monitor, for cross-node advisories.

·         ADR command-line tool - The Oracle Automatic Diagnostic repository (ADR) has a new command-line interface dubbed ADRCI, the ADR Command Interface. 

·         Optimized RAC cache fusion protocols – This moves on from the general cache fusion protocols in 10g to deal with specific scenarios where the protocols could be further optimized.

·         Oracle 11g RAC Grid provisioning - The Oracle grid control provisioning pack allows you to "blow-out" a RAC node without the time-consuming install, using a pre-installed "footprint". 

·         RAC Hot patching - Zero downtime patch application.

Now that we see the features, let’s review a best practices checklist for migrating to 11g.

Oracle Migration checklist

Oracle 11g migration due diligence recognizes that Oracle is the world's most flexible and robust database, and upgrading can be very tricky.  Prior to putting your Oracle 10g upgrade into production, it's a best practice to perform complete testing and obtain an independent Oracle health check to ensure an optimal configuration. 

Remember you can use the v$system_fix_control  view to display specific optimizer features by release.

One common complaint about a haphazard migration strategy is varying performance after migration.  New bugs are found and old bugs are fixed and while overall performance will be faster, you need to ensure proper testing to avoid surprises.  I recommend checking these items prior to migrating to production in 11g:

·         Selectively disable dynamic sampling - Dynamic sampling is not for every database.  Dynamic sampling default levels change between releases, and you may want to turn-off dynamic sampling, depending on your database load.

·         Re-set optimizer costing - Consider unsetting your CPU-based optimizer costing base upon your workload characteristics.  CPU costing is best of you see CPU in your top-5 timed events in your STATSPACK/AWR report, and the 11g default of _optimizer_cost_model=cpu will include CPU costs, sometimes invoking more full scans, especially in tablespaces with large blocksizes. 

·         Verify quality of CBO statistics - Oracle does automatic statistics collection and your original customized dbms_stats job (with your customized parameters) will be overlaid.  You may also see a statistics deficiency (i.e. not enough histograms) causing performance issues.  Re-analyze object statistics using dbms_stats and make sure that you collect system statistics. 

·         Check optimizer parameters - Ensure that you are using the proper optimizer_mode (the default of all_rows which is not optimal for online transaction processing systems).

·         Check I/O timings – When using ASM, beware that "db file scattered reads" (full scan I/O) can become slower than "db file scattered reads" (usually single block gets) because of non-contiguous data block placement on disk. 

In sum, migration to 11g can be seamless or full of surprises, it’s your choice.  A proper 11g migration requires careful up-front planning with an eye towards upgrading all of the infrastructure components that go along with Oracle and choosing those new 11g features that are right for you!

NOTE: Rampant author Laurent Schneider has some additional insight into creating an Oracle Automatic Diagnostic Repository (ADR)


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