Troubleshooting: 'Log file sync' Waits (Doc ID 1376916.1)

Last updated on JULY 17, 2024

Applies to:

Gen 1 Exadata Cloud at Customer (Oracle Exadata Database Cloud Machine) - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Oracle Database Backup Service - Version N/A and later
Oracle Database Cloud Exadata Service - Version N/A and later
Oracle Database Cloud Service - Version N/A and later
Information in this document applies to any platform.

Purpose

The purpose of this note is to help troubleshoot issues where there are significant waits for the event 'log file sync'.

Troubleshooting Steps

	To view full details, sign in with your My Oracle Support account.
	Don't have a My Oracle Support account? Click to get started!

In this Document

Troubleshooting Steps

What is a 'log file sync' wait?

What should be collected for initial diagnosis of 'log file sync' waits ?

What causes high waits for 'log file sync'?

Issues affecting LGWR's IO Performance

Compare the average wait time for 'log file sync' to the average wait time for 'log file parallel write'.

Recommendations

Effect of Peaks of IO (or Bursts of IO) on 'log file sync' waits

Check LGWR Traces

Recommendations

Check to see if redo logs are large enough

Recommendations

Excessive Application Commits

Compare the average user commits and user rollbacks to user calls

Recommendations

Other Wait Events that may be relevant

Adaptive Log File Sync

Redo Synch Time Overhead

Other diagnostics to help analyze 'log file sync' waits?

Data Guard and 'Log File Sync'

Troubleshooting Other Performance Issues

Community Discussions

My Oracle Support provides customers with access to over a million knowledge articles and a vibrant support community of peers and Oracle experts.