Wait Events and Potential Causes
Wait Event | General Area | Possible Causes | Look for / Examine |
---|---|---|---|
| Buffer cache, DBWR | Depends on buffer type. For example, waits for an index block may be caused by a primary key that is based on an ascending sequence. | Examine |
| Buffer cache, DBWR, I/O | Slow DBWR (possibly due to I/O?) Cache too small | Examine write time using operating system statistics. Check buffer cache statistics for evidence of too small cache. |
| I/O, SQL statement tuning | Poorly tuned SQL Slow I/O system | Investigate |
| I/O, SQL statement tuning | Poorly tuned SQL Slow I/O system | Investigate |
| Locks | Depends on type of enqueue | Look at |
| Latch contention | SQL parsing or sharing | Check |
| Log buffer, I/O | Log buffer small Slow I/O system | Check the statistic |
| I/O, over- committing | Slow disks that store the online logs Un-batched commits | Check the disks that house the online redo logs for resource contention. Check the number of transactions ( |
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Oracle-Wait Events and Potential Causes
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