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12c inmemory

inmemory: Why did that table was not populated in the column store?

I enabled an huge 70G table for inmemory population, I expected the inmemory population to take a while, but the population didn’t complete even after letting it run for a day. Why?

ASH data

Initial review of the server shows no issues, no resource starvation. This must be a problem with Oracle processes itself. I started digging further, and ASH data shows that in numerous samples the process was seen reading block using single block I/I calls. Also object_id matches with the table I was trying to populate.

inmemory: sa00 process

After the restart of a 12c inmemory database with 300GB+ SGA, I noticed that an Oracle background process sa00 was consuming a bit of CPU. Documentation suggests that it is SGA Allocator process, however, ipcs -ma command shows that the shared memory segment is already allocated. I was curious, of course, what would that background process will be allocating?.


Process stack of the process shows that it is touching SGA pages to pre-page SGA memory pages.

Inmemory: Not all inmemory_size is usable to store tables.

I have been testing the inmemory column store product extensively and the product is performing well for our workload. However, I learnt a bit more about inmemory column store and I will be blogging a few them here. BTW, I will be talking about internals of inmemory in Oaktable world presentation, if you are in the open world 2014, you can come and see my talk: