Oracle gives Log read is SYNCHRONOUS though disk_asynch_io is enabled!
Hi,
We have a Oracle 11.2.0.2.0 64 bit database on a SuSe 10 server (with NFS mounts) and in some trace file I did found the following message:
Log read is SYNCHRONOUS though disk_asynch_io is enabled!
I'm puzzled because Async Io is enabled:
filesystemio_options is set to SETALL and disk_async_io is set to TRUE. When I query:select file_no,filetype_name,asynch_io from v$iostat_file;
I get the following:
FILE_NO FILETYPE_NAME ASYNCH_IO
---------- ---------------------------- ---------
0 Other ASYNC_OFF
0 Control File ASYNC_OFF
0 Log File ASYNC_OFF
0 Archive Log ASYNC_OFF
0 Data File Backup ASYNC_OFF
0 Data File Incremental Backup ASYNC_OFF
0 Archive Log Backup ASYNC_OFF
0 Data File Copy ASYNC_OFF
0 Flashback Log ASYNC_OFF
0 Data Pump Dump File ASYNC_OFF
all datafiles: async_on!
The NFS mount options for all filesystems are correct: rw,v3,rsize=32768,wsize=32768,hard,nolock,timeo=600,proto=tcp,sec=sys
Is IO for log file allways synchrounous? The reason for my question is that we see from time to time the following Awr information:
Top 5 Timed Foreground Events
Event Waits Time(s) Avg wait (ms) % DB time Wait Class
log file sync 62,576 32,908 526 67.98 Commit
db file sequential read 539,144 11,033 20 22.79 User I/O
DB CPU 3,800 7.85
enq: TX - row lock contention 375 693 1848 1.43 Application
Log archive I/O 667 59 89 0.12 System I/O
During this high log file sync users complain about bad performance.
Any ideas?
regards,
Ivan