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blocking LCK_M_SCH_S, LCK_M_SCH_M Expand / Collapse
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Posted Wednesday, February 12, 2014 12:55 PM
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opc.three (1/10/2013)

"Mostly Online" feels like ~60%. I'd submit "Near Online", it feels closer to 99%


until today, all my "online" index rebuilds worked as expected. but just today I got a series of transactions running and SQL is not able to get the LCK_M_SCH_M and end the rebuild.

so, for me, today it feels as "not exactly online index rebuild". I would put it at 10%.
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Posted Wednesday, February 12, 2014 11:06 PM


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mauriciorpp (2/12/2014)
opc.three (1/10/2013)

"Mostly Online" feels like ~60%. I'd submit "Near Online", it feels closer to 99%


until today, all my "online" index rebuilds worked as expected. but just today I got a series of transactions running and SQL is not able to get the LCK_M_SCH_M and end the rebuild.

so, for me, today it feels as "not exactly online index rebuild". I would put it at 10%.

If you had 1 failure out of 10 tries equating to 10% then by that accounting you can reasonably look forward to 90 error-free online rebuilds before your next failure...on average

Seriously though, the 99% was not meant to be thought of as a success-rate. If you have a very busy system, even though the rebuild only asks for short-lived stability-type locks at the beginning and end of the rebuild, i.e. the rebuild displays properties of an online process during 99% of its operations and only displays offline properties for 1% of its operations, you can still run into problems during that 1% on a very regular basis on a busy system.


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Post #1541026
Posted Thursday, February 13, 2014 4:17 AM
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you are correct, @opc.three. I just wanted to point out that even the unexpected should be expected at some point in time, given a large enough installed base.

I had to schedule this index rebuild, it took almost an hour to be able to hold a schema lock for 1 second (the table is small, around 25mb), but it worked after all!
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