I have been contacted by one of our customers to provide reference information on troubleshooting Oracle Log File Sync waits.
I think that this information worth short blog post.
- Log File Sync waits occur when sessions wait for redo data to be written to disk
- typically this is caused by slow writes(IO subsystem saturation,…)
- spikes in Log File Parallel Write, as shown by James Morle
- or the application is committing too frequently
- improper Operating System configuration(check 169706.1)
- CPU overburning(very high demand => LGWR on run queue, check Kevin Closson post)
- high Log Parallelism, which saturates filesystem/OS, as investigated by Nikolay Savvinov
- BUGs in Oracle(especially with RAC option) and 3rd Party software(like ODM/DISM)