High Buffer busy waits during log switches
(Doc ID 1577905.1)
Last updated on FEBRUARY 01, 2022
Applies to:
Oracle Database - Enterprise Edition - Version 10.2.0.5 to 11.2.0.4 [Release 10.2 to 11.2]Oracle Database Cloud Schema Service - Version N/A and later
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 Exadata Express Cloud Service - Version N/A and later
Information in this document applies to any platform.
Symptoms
When the log switches happen the instance experiences High buffer busy waits for DML transactions.
AWR report shows the sudden Buffer Busy waits spiking up |
---|
Top 5 Timed Foreground Events Event Waits Time(s) Avg wait (ms) % DB time Wait Class db file sequential read 1,214,478 4,843 4 37.27 User I/O DB CPU 2,581 19.87 buffer busy waits 598 1,552 2596 11.95 Concurrency direct path read temp 98,197 651 7 5.01 User I/O log file sync 26,889 147 5 1.13 Commit |
ASH Reports shows High Buffer Busy waits on DML statements. |
---|
Top SQL with Top Events SQL ID % Event Top Row Source % RwSrc SQL Text zzzzzzzzzzzz buffer busy waits 3.13 ** Row Source Not Available ** 3.13 INSERT INTO TABLE_xxxxx (O... zzzzzzzzzzzz enq: TX - index contention 1.01 ** Row Source Not Available ** 1.01 INSERT INTO xxxxxxx (O... wwwwwwww buffer busy waits 2.64 ** Row Source Not Available ** 2.64 INSERT INTO TABLE_wwwwww(O... |
The manual log switches "alter system archive log current" or implicit log switch can cause this high buffer busy waits spike.
Changes
The instance uses a product called 'SafeNet Luna' for their HSM which is a key store for external TDE module for the tablespace encryption.
Safenet is configured for HA, which means that one of the 'Safenet Servers' is actually at a remote WAN-Based location - so depending on availability of the local Safenet server, a request may be redirected to go over the WAN.
Cause
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
Symptoms |
Changes |
Cause |
Solution |
References |