Adaptive Switching Between Log Write Methods can Cause 'log file sync' Waits
(Doc ID 1462942.1)
Last updated on JULY 15, 2020
Applies to:
Oracle Database Cloud Schema Service - Version N/A and laterOracle Database Exadata Cloud Machine - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Oracle Database Cloud Exadata Service - Version N/A and later
Oracle Database Backup Service - Version N/A and later
Information in this document applies to any platform.
Symptoms
- The database version is 11.2.0.3
- The log writer process on the database is blocking most of the other sessions and taking an average wait time of 10ms to commit.
- On checking the hardware, the I/O wait time is very small from the hardware side
- This means that all the time is on CPU processing the request.
- Database is OLTP-based and has high commits/second
- The same issue did not occur in 10g.
- The problem seems to 'go away' temporarily after the database is restarted but ultimately returns after a few days.
- AWR may show 'log file sync' waits as the highest wait:
Changes
The database was upgraded from 10.2.0.4 to 11.2.0.3.1.
Cause
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In this Document
| Symptoms |
| Changes |
| Cause |
| Solution |
| References |