| Wait Problem | Potential Fix |
| Sequential Read | Indicates many index reads—tune the code (especially joins) |
| Scattered Read | Indicates many full table scans—tune the code; cache small tables |
| Free Buffer | Increase the DB_CACHE_SIZE; shorten the checkpoint; tune |
| Buffer Busy | Segment header—add freelists or freelist groups |
| Buffer Busy | Data block—separate “hot” data; use reverse key indexes; use |
| Buffer Busy | Undo header—add rollback segments or areas |
| Buffer Busy | Undo block—commit more; larger rollback segments or areas |
| Latch Free | Investigate the detail (a listing later in this chapter includes fixes) |
| Enqueue – ST | Use LMTs or preallocate large extents |
| Enqueue – HW | Preallocate extents above the high water mark |
| Enqueue – TX4 | Increase initrans or use a smaller block size on the table or index |
| Enqueue – TX6 | Fix the code that is making the block unsharable (use v$lock to find) |
| Enqueue – TM | Index foreign keys; check application locking of tables |
| Log Buffer Space | Increase the log buffer; use faster disks for the redo logs |
| Log File Switch | Archive destination slow or full; add more or larger redo logs |
| Log file sync | Commit more records at a time; use faster redo log disks; use |
| Write complete waits | Add database writers; checkpoint more often; buffer cache too small |
| Idle Event | Ignore it |
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Oracle wait problems and potential solutions
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