October 27, 2010 at 11:54 pm
dm_os-wait_stats gives dbmirroring_cmd having highest wait time. mirroring is set in high safety mode. Will the waiting reduce if i change to async mode? Average wait time is abt 1 ms. Should i worry about it? Also, is it possible to get min and max wait times for this wait type?
October 28, 2010 at 2:55 am
I ran Glen Barry's code and found that about 95% of waits is due to dbmirroring_cmd wait type.
dm_os_wait_stats gives this figure.
wait type count wait time max wait signal wait
DBMIRRORING_CMD 289259731437107033623640484500
max wait is 3623 sec. Does this mean some mirroring thread had to wait for these many seconds? Also Average wait time is 1 sec. is this ok for an OLTP system?
Also can someone provide me more information on dbmirroring_wait type.
I read somewhere that this wait is due to waiting for a record to be hardened to the disk in the log file.
This leads to conclusion that this wait type will be lesser if mirroring is in async mode since principle doesnt have to wait for mirror's ack. Am i right here?
October 28, 2010 at 6:40 am
Another link says dbmirroring wait are coz the threads have nothing to do and hence they wait. This is in contrast to what was written in a diff thread that they signify they are waiting for log records to be written.
http://sqlserver.quest.com/thread.jspa?threadID=12198
I too think what's written in this link *may* be correct considering the fact that my max wait time is 3000 secs which can not be true if it were waiting for a transaction to be written to the log file.
Any confirmation on this?
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