Statspack: High log file sync timeouts and waits

Question

Hi all,
Please see an extract from our statpack report:
Top 5 Timed Events
~~~~~~~~~~~~~~~~~~ % Total
Event Waits Time (s) Ela Time
log file sync 349,713 215,674 74.13
db file sequential read 16,955,622 31,342 10.77
CPU time 21,787 7.49
direct path read (lob) 92,762 8,910 3.06
db file scattered read 4,335,034 4,439 1.53
Avg
Total Wait wait Waits
Event Waits Timeouts Time (s) (ms) /txn
log file sync 349,713 150,785 215,674 617 1.8
db file sequential read 16,955,622 0 31,342 2 85.9
I hope the above is readable. I'm concerned with the very high number of Waits and Timeouts, particulary around the log file sync event. From reading around I suspect that the disk our redo log sits on isn't fast enough.
1) Is this conclusion correct, are these timeouts excessively high (70% seems high...)?
2) I see high waits on almost every other event (but not timeouts), is this pointing towards an incorrect database database setup (give our very high loads of 160 executes second?
Any help would be much appreciated.
Jonathan

Answer 1

Top 5 Timed Events
~~~~~~~~~~~~~~~~~~ % Total
Event Waits Time (s) Ela Time
log file sync 349,713 215,674 74.13
db file sequential read 16,955,622 31,342 10.77
CPU time 21,787 7.49
direct path read (lob) 92,762 8,910 3.06
db file scattered read 4,335,034 4,439 1.53
Avg
Total Wait wait Waits
Event Waits Timeouts Time (s) (ms) /txn
log file sync 349,713 150,785 215,674 617 1.8
db file sequential read 16,955,622 0 31,342 2 85.9What's the time frame of this report on?
It looks like your disk storage can't keep up with the volume of I/O requests from your database.
The first few thing need to look at, what're IO intensive SQLs in your database. Are these SQLs doing unnecessary full table scan?
Find out the hot blocks and the objects they belong.
Check v$session_wait view.
Is there any other suspicious activity going on in your Server ? Like other program other than Oracle doing high IO activities? Are there any core dump going on?