how to change the read cache memory size for hashfile

zulfi123786 · Post by **zulfi123786** » Mon Sep 28, 2009 4:24 am

the default size is 128 mb, how can i change this setting to a higher value for better performance?

ArndW · Post by **ArndW** » Mon Sep 28, 2009 5:02 am

Chances are very, very high that your job's bottleneck is not in reading a hashed file but somewhere else, thus changing buffer and cache sizes, if possible, would not make a difference.

Are you asking about reference reads, or perhaps writes? Also, perhaps you might be looking at public/private link caching - which one might it be?

chulett · Post by **chulett** » Mon Sep 28, 2009 7:01 am

Are you asking how can you change it or how can you know what to change it to? And are you thinking about changing the default?

Be very careful there, it can have quite unexpected consequences.

ray.wurlod · Post by **ray.wurlod** » Mon Sep 28, 2009 7:16 am

What makes you believe that larger buffer sizes relate to "performance" (whatever that is) being improved?

zulfi123786 · Post by **zulfi123786** » Mon Sep 28, 2009 7:31 am

I am doing a look up on a hashfile and in log i can see that it is Private caching.....
What is the difference between Private caching and public caching???

ArndW · Post by **ArndW** » Mon Sep 28, 2009 7:34 am

There is a whole PDF documenting the differences and link caching functionality, but in most cases it is not necessary to turn on this functionality. Just load your hashed lookup file to memory (just those columns you intend on using) and DataStage will, in almost all cases, do a quick and good job for you.

zulfi123786 · Post by **zulfi123786** » Tue Apr 06, 2010 3:39 am

ArndW wrote:There is a whole PDF documenting the differences and link caching functionality.

In which datastage document is it discussed? I cant find anything in the server job developer guide

ray.wurlod · Post by **ray.wurlod** » Tue Apr 06, 2010 3:49 am

dsdskche.pdf

I can't remember what the title of the manual is.

chulett · Post by **chulett** » Tue Apr 06, 2010 5:26 am

Technical Bulletin, Part No. 00D-TB003, Hash Stage Disk Caching