Wait for Event Log wait event Solution

I insisted on reading three sets of RAC AWR every day and summarized it.

Query the SQL statement of the log wait event:

9i: Select * from V $ event_name where name like '% log %'; (about 14)
10g: Select name, wait_class from V $ event_name where name like '% log %'; (about 35)
11G: Select name, wait_class from V $ event_name where name like '% log %'; (about 30)

The following are the most common examples:

I,Log File switch (archiving needed) 

That is, when the log is switched to the target log group, archiving is not yet completed. You must wait.

 Possible causes:Redo,ArchivePartitionPoor I/O performanceSlow archiving and writing, and unreasonable setting of the number of log groups 

Solution: 1, Increase the size of the log group or log group members

2, Adjust archive log to a disk with high Io performance, such as storage

3, AdjustmentLog_archive_max_processesParameters

 II,Log File switch (checkpoint incomplete) 

Indicates that the dirty data protected by the log group has not been written to the target log group during log switching. 

Possible causes:DbwnWriting is too slow,I/OProblems 

Solution: 1, Add additionalDbwn

2, Increase the size of the log group or log group member

 III,Log File sync 

Possible causes: LgwrLow write efficiency,CommitToo frequent 

Solution: 1, ImproveLgwrWrite efficiency, using disks with good Io Performance

2Batch submission,(Real-time online business operations with caution)

3, UseNologging/unreoverableOption () 

IV,Log File single write 

Cause:Wait for the log file header to be updated 

V,Log File parallel write 

Cause:Waiting for concurrent writing to multiple log group members 

VI,Log buffer space 

Cause:Database-generated log ratioLgwrThe log writing speed is fast, or the log switching speed is too slow. 

Solution: 1, IncreaseLog Buffer

2, DiskI/OBottlenecks

Note: The DB plan is a redo partition, and the hard disk occupied by the arch partition space should be RAID 1 as much as possible.

To be continued