Hash File lookup query

Satheesh_Yama · Post by **Satheesh_Yama** » Wed Aug 02, 2006 9:08 am

Hi Dsxians,

I am using three hash files in a job,each having millions of records,i would like to know if i enable preload file into memory option for all the three hash lookups will it cause overflow of memory there by causing job to abort or performance issue.Please let me know ur views.

Thanks
satheesh

kris007 · Post by **kris007** » Wed Aug 02, 2006 9:20 am

Option "Preload to memory" is best to use when you use the rows in the hashed file more than once i.e. the rows from the primary input find hits in the hashed files on more than one occassion. In your case, IMO don't use that Option if you look up at the values in hashed file only once or very few times, and also as it would also exhaust the memory resources.

IHTH

chulett · Post by **chulett** » Wed Aug 02, 2006 9:29 am

Actually, all you should "lose" is a little time. No abort or permance issue other than what you've already got with a large hashed file read directly from disk. Checking that option means it will try to cache it into memory and, when it can't, it will note that in the log.

So if you know it will never fit into cache, then best to not check that option so it doesn't spend the time to try.