Re: very low hit ratio

> we have a data warehouse type of database and I noticed that buffer
> cache hit ratio is very low: db block gets 37,173,962; consistent gets
> 349,994,093; physical reads 888,341,652. Is this normal in a
> datawarehouse environment? Thanks.

It could be "normal" or it could not be. It depends on what your end users are doing. Are they running tools which let them perform ad-hoc queries? If so, then they could be accessing data that never gets accessed by others, therefore blocks in the buffer cache don't get reused like they would in an OLTP environment. Then again, if they are running some software and querying the same tables over and over again, then your buffer cache might need to be bigger. The big thing here is to look at how the users are accessing the data and try to determine how to best meet their requirements.

HTH,
Brian

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