The plan of an SQL can change, and the change is justified if it doesn’t degrade performance. Changes in the values of bind variables, change in statistics etc. can change the plan which is often an expected behavior. But now and then you may see a change that degrades performance. Below script compares the plans for SQL s from […]
Following is a brief account of some serious issues we had with DRM on a 3 node RAC system running 11g R2. We had intermittent spikes that were severe enough to disrupt service. Here is a section from a 10-minute ASH showing DRM related wait “gcs drm freeze in enter server mode.” Our first attempt was to disable DRM by setting _gc_policy_time=0. […]
RAC Wait event gc buffer busy acquire indicates that the session experiencing this event is waiting on another session on the same instance to release the block. Basically the waiting session is not able to pin a block, and will wait on this event until it can pin the block. (gc buffer busy release means […]
In the context of database processing, tuning can be defined as a set of techniques that helps the database to operate more efficiently–with higher throughput. Database tuning can be at the SQL statement level, or at the system level. SQL Tuning SQL Tuning is a set of techniques used to execute the SQL in the […]
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