19C rac有大量的LOG FILE SYNC等待事件

郑全

Database is upgraded from 11.2 to 19c, then there is a change in LGWR architecture from 12c onwards by using parallel adaptive LGWR. This might cause slow LGWR throughput sometimes causing 'log file sync' waits in 19c for foreground sessions. This is due to some bug with adaptive behavior of parallel LGWR to serial LGWR and vice versa.

Solution: Evaluate the new LGWR architecture (enabled by default) in UAT before PROD. To use the old LGWR architecture, set the below parameter:

_use_single_log_writer=TRUE /* default value: ADAPTIVE */

Note: This is NOT a dynamic parameter. It requires database bounce.