Oracle library cache tuning – A Real Case Study.

I have made a few comments in previous posts about the latch: library cache and playing with cursor parameters that can introduce surprises; Here is another one library cache tuning – A Real Case Study. Scenario : Users started complaining about very poor application performance, hung and incomplete transactions. Some severity one ticket for immediate […]

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Oracle Hanganalyze Performance Problems “sqlplus -prelim”

Hanganalyze / Librarycache contention Last week I was called up to  help to resolve one of the production database hung issue. This totally screwed the database by all means  [ Database connections were hanging, Connections on the server using SQL*Plus as sysdba was also hanging, EM grid was spinning ] Dammn totally stuck …. you […]

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Oracle DBA Silver Bullets – Performance Queries

Just thought to share few queries from my repository. It may be useful for all new DBAs. Of course these are quite old ones and you can do most of them through Enterprise Manager, still we DBAs always like command line 🙂 Show sessions that are blocking each other : select ‘SID ‘ || l1.sid […]

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Tips to Maximize performance and scalability of Oracle E-business Suite 11i

Application Tier: Forms Forms performance issues may arise when dead connection persists on the server and consuming the server resources. Enable the forms dead client connection can eliminate the dead connection. FORMS60_TIMEOUT=10 (recommended value and value specified in minutes) Do $ ps –ef| grep f60webmx and terminates f60webmx processes for dead clients. Enable Forms Abnormal […]

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Oracle Performance Tuning – How to Use AWR ?

Here are few silver bullets to use AWR for diagnosing performance issues ….. AWR – Automatic Workload Repository Detailed & comprehensive performance history Based on “snapshot” (time interval) Automatic Database Diagnostic Monitor (ADDM) About 79 DBA_HIST_* “tables” Defaults: Hourly snapshots Weekly retention (month is better) Overview of important AWR tables DBA_HIST_SNAPSHOT PK: SNAP_ID DBID, INSTANCE_NUMBER […]

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Tuning High CPU Consumption on Oracle server

For any performance tuning issue, our strategy in diagnosing the problem is to take a “top-down” approach and follow the trail of highest CPU consumption down to the offending processes, and eventually the offending sessions and query. Verify CPU Consumption on the server is the first step any DBA should do for a top-down approach […]

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Tuning indexes on RAC environments-4

Excessive undo block shipment and contention for undo buffers I have seen this scenario in one my projects where  Oracle EBS workload is high. When a select statement needs to read a block with active transactions, it has to cleanout the block and undo the changes to create a CR version. If the active transactions […]

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Tuning indexes on RAC environments-3

Reversing the index key This is accomplished by executing the following SQL statement: ALTER INDEX <index_name> REBUILD REVERSE; A reverse key index will invert the bytes of the index key column, so that values originally stored in the same block may be spread across multiple index leaf blocks. That will reduce buffer busy contention especially […]

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Tuning indexes on RAC environments-2

Globally busy buffers due to contention for index leaf and branch blocks As we discussed in previous sessions, because of batch INSERT high concurrency could occur for a relatively small set of index leaf and branch blocks, where index keys are populated with monotonically ascending values.The symptoms are increased frequencies and wait times for a […]

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Tuning indexes on RAC environments-1

Introduction and Significance of tuning indexes in RAC environments. Oracle E-Business environment with financial modules like AP and GL having large scale payment invoices transaction. Let me take example of one my public sector clients, they do process of 3 million payment instructions every night. Such most insert intensive applications running on RAC the frequency […]

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Index Performance Tuning Techniques for RAC

It’s been quite some time since my readers are requesting to see some posts on RAC performance tuning concepts and practices. In the process of testing some of the tuning techniques, as well as discussing and interpreting the results, I am preparing a four-day in depth session to understand index performance tuning techniques for RAC. […]

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Gather Schema Statistics with LASTRUN Option does not Clean FND_STATS_HIST Table

After running Gather Schema Statistics concurrent request with (LASTRUN) option to save only the history for last run, then run the concurrent request again for 2 times after that found that (FND_STATS_HIST) tables contains the history for all the 3 requests and it is not cleaned up to keep only last run. Sample steps to […]

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