lookup on hash file

dr46014 · Post by **dr46014** » Fri Dec 15, 2006 11:19 am

hi
i have approximately 10000 records in a hash file and i am doing a look up on this hash file for populating the target tables.i am getting update for the hash file every 15days.so how can i refesh my hash file so that look up will be effective.i dont want to use ODBC for look up

DSguru2B · Post by **DSguru2B** » Fri Dec 15, 2006 11:22 am

Build the hashed file again. This way it will be refreshed by the most currect records.

dr46014 · Post by **dr46014** » Fri Dec 15, 2006 11:25 am

ok thanks

ray.wurlod · Post by **ray.wurlod** » Fri Dec 15, 2006 3:23 pm

Enable write cache when (re-)populating your hashed file. It makes a notable difference.

Dsnew · Post by **Dsnew** » Fri Dec 15, 2006 3:56 pm

Ray, When you said "Enable write cache"
Does that mean check the "Allow stage write cache"

Also in a hashed file when do you use - Pre-loadfile to memory?

I_Server_Whale · Post by **I_Server_Whale** » Fri Dec 15, 2006 4:00 pm

Dsnew wrote:Ray, When you said "Enable write cache"
Does that mean check the "Allow stage write cache"

Also in a hashed file when do you use - Pre-loadfile to memory?

1. Yes.

2. You pre-load a hashed file to memory when the size of the hashed file is low and it greatly improves the performance of a lookup since the hashed file will be in memory and disk I/O is avoided.

Whale.

Dsnew · Post by **Dsnew** » Fri Dec 15, 2006 4:03 pm

Thanks for the info, Naveen :D

ray.wurlod · Post by **ray.wurlod** » Fri Dec 15, 2006 4:17 pm

1. Yes
2. Yes, unless updating the same hashed file in the same job. In which case disable both write and read cache (since they're separate caches). If the hashed file is tiny (say less than 10 groups) I probably wouldn't bother with read cache either, as its pages are likely to be memory resident in any case.