Re: strange oradebug from log file sync wait
- From: Niall Litchfield <niall.litchfield@xxxxxxxxx>
- To: oracledbaquestions@xxxxxxxxx
- Date: Sat, 28 May 2011 07:17:39 +0100
What are the lfs values? Also CPU usage on box? Lfs going south can be due
to i/o subsystem issues (seen it with failed disk on RAID5 and dead battery
for cache on SAN) but can also be CPU starvation.
On 27 May 2011 13:42, "Dba DBA" <oracledbaquestions@xxxxxxxxx> wrote:
DB: 11.1.0.7
HP-Unix
We have a database used for ETL/data loads and then the data is fed to an
oltp. We had performance issues on it yesterday and noticed that the waits
were on log file sync. The day before we did a comparable data load without
issue. So we ran an AWR report during each period and a differential awr
report. We noticed that the day before we were handling 50% more redo/second
during a similiar load and time of day. Nothing has changed. We looked at
other waits and nothing else seems to be standing out. From there we ran an
oradebug hanganalyze 2 and noticed something odd. It seems that the chains
are all pointing back to the asynchronous IO. We have run 10046 trace to
look at timing events on the waits and they appear to be longer than they
should. We have referred this back to the system admins to see what they can
tell us.I tried to google around and look on the oracle support site, but I
do not see much about the async disc IO event. There is an oracle background
process that strictly has this event and when I ran a 10046 trace on it, I
did not see anything that would immediately lead me to believe there are
issues. oracle support does briefly mention a bug related to ksfd
immediately after a patch, but we have not applied a patch recently.
Has anyone seen a hang analyze like this?
Chains most likely to have caused the hang:
[a] Chain 1 Signature: 'ksfd: async disk IO'<='log file sync'
Chain 1 Signature Hash: 0x1016ca92
Chain 2 Signature: 'ksfd: async disk IO'<='log file sync'
Chain 2 Signature Hash: 0x1016ca92
[c] Chain 3 Signature: 'ksfd: async disk IO'<='log file sync'
Chain 3 Signature Hash: 0x1016ca92
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