A few basic notes on Oracle Database Administration.

Sunday, July 6, 2008

I'm beginning to distrust Oracle

I am learning that I have been trusting Oracle too much. I have figured that Oracle has top rate developers, so when they offer a facility like ASMM or GATHER_STATS_JOB. I assume that it will be done well.

Now I am learning that ASMM has been allocating our shared pool too large, and has been adjusting sizes not once an hour, but once a minute.

I am not happy with the statistics that the 'wonderful' automatic GATHER_STATS_JOB has been collecting. Also the job has been causing contention with some of our production jobs.

The one that seems really strange to me is Log_buffer. I allocated 28M to log_buffer. According to Oracle, LGWR should be writing, at a maximum, when log_buffer is 1M full. Instead, I see that it is writing 2M at a time. I am going to have to figure that one out.

I expect that when Oracle offers to automate these processes, that this is their own product, so the calculations will be well done. I expected, but I am wrong.


Noons said...


an ounce of distrust is worth more than a ton of blind trust!

Bradd Piontek said...

Automatic Memory Management has a slew of 'bugs' or maybe they are 'features' written against it (specifically in 10g). I have heard certain nameless experts say to set shared_pool_size, java_pool_size, large_pool_size, and db_cache_size with AMM, and it will act as the floor for those settings.

Anyway, anything with the word 'automatic' in it should be looked in to and understood.