uvconfig 64 bit files

roy · Post by **roy** » Mon Nov 08, 2004 4:19 am

Hi All,
Does anyone know of any issues regarding change in uvconfig so hash files are generated with 64 bit instead of 32?
I plan to do it, but was wondering if it might cause problems with working jobs which currently run with the 32 bit hash files configuration.

any advice built on experiance you have doing this is helpfull.

Thanks in advance,

chulett · Post by **chulett** » Mon Nov 08, 2004 8:22 am

Well, there have been several posts on the subject by the likes of Ray and Ken, who counsel that it is generally Not A Good Idea. This makes all hash files 64 bits, including the internal hashes used by the engine.

That being said, from what I recall it would only affect any new hash files created after the configuration file was changed and the engine regened. It should have no effects on existing 32 bit hash files. Downside? Unnessary overhead, hash files being created as 64 bit that have no need to be. Seems to be best to create just the hash files that need to be that way as 64 bit and leave the rest alone.

As long as you understand how it all works, and it's what you want to do, then...

ray.wurlod · Post by **ray.wurlod** » Mon Nov 08, 2004 2:49 pm

Craig summed it up well. Things will not break, if that's what you were concerned with.

However, there is a computational penalty (recall that DataStage is primarily a 32-bit environment, so has to construct 64-bit numbers) as well as a space penalty (there are three or five pointers per record, so that's a 12-byte or 20-byte penalty per record compared to 32-bit hashed files).

Best practice is to leave the uvconfig parameter 64BIT_FILES off, and create 64-bit hashed files explicitly where you need them.

BTW the Hashed File Calculator does take the different internal storage overheads into account when calculating the number of groups.

roy · Post by **roy** » Mon Nov 08, 2004 4:12 pm

Thanks guys,
I'll take your advice and go for the need to be 64 bit aproach.
I also poped this question for support so if they come up with some interesting insight, not yet said, I'll post it (as I hope others will do with their posts).

Cheers

,

Titto · Post by **Titto** » Wed Oct 26, 2005 12:02 pm

ray.wurlod wrote:Craig summed it up well. Things will not break, if that's what you were concerned with.

However, there is a computational penalty (recall that DataStage is primarily a 32-bit environment, so has to construct 64-bit numbers) as well as a space penalty (there are three or five pointers per record, so that's a 12-byte or 20-byte penalty per record compared to 32-bit hashed files).

Best practice is to leave the uvconfig parameter 64BIT_FILES off, and create 64-bit hashed files explicitly where you need them.

BTW the Hashed File Calculator does take the different internal storage overheads into account when calculating the number of groups.

any idea how to create 64-bit hash files explicitly for a single DS Job??

ray.wurlod · Post by **ray.wurlod** » Wed Oct 26, 2005 5:19 pm

Not possible using the Options button in the Hashed File stage.

You need either to create them using the Hashed file stage then RESIZE to 64-bit, or to create them manually as 64-bit. For the latter you can copy the command from the Hashed File Calculator.

<losing battle>
It's HASHED file, not hash file.
</losing battle>