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DCWRITEDAEMON
Posted: Wed Aug 25, 2004 1:16 am
by anupam
What should be the ideal value for "DCWRITEDAEMON"??
How does the write daemon pause between writes effect the performance.
Re: DCWRITEDAEMON
Posted: Wed Aug 25, 2004 7:09 am
by sanjay
ideal value should be 20000
anupam wrote:What should be the ideal value for "DCWRITEDAEMON"??
How does the write daemon pause between writes effect the performance.
Posted: Wed Aug 25, 2004 4:26 pm
by ray.wurlod
On a single CPU machine DCWRITEDAEMON should not be set too low (say not below 10). This is the multiple of 10 milliseconds that the daemon pauses between writes.
On a multiple CPU machine lower values are OK.
High values, like the 20000 suggested by sanjay, mean that it can take up to 200 seconds (that's over 3 minutes) for a write to a cached hashed file to be flushed to disk - way too long in my opinion.
Full details are to be found in the Technical Bulletin Hashed Stage Disk Caching (dsdskche.pdf), which is one of the DataStage manuals. In particular, consult the section called Considerations for Performance.
Posted: Sat Sep 04, 2004 1:34 am
by anupam
We are having 24 CPU Sun Microsystems sun4u Sun Fire 6800 Server. What should be the value DCWRITEDAEMON for this kind of server.
What are the dependent things which are going to be effected once we make changes in this parameter.
Are there any other associated parameters also which needs to be changed along with this parameter to get better performance.
Posted: Sat Sep 04, 2004 5:36 pm
by ray.wurlod
10. This means that the writer daemon pauses 100 milliseconds after each write.
There are no dependencies, unless you need immediate update of the hashed file, in which case you probably want to use private link cache rather than shared cache.
Except, of course, that DCWRITEDAEMON must be 1 for this mechanism to work at all.
Posted: Sun Sep 05, 2004 12:27 am
by desais_2001
ray.wurlod wrote:10. This means that the writer daemon pauses 100 milliseconds after each write.
There are no dependencies, unless you need immediate update of the hashed file, in which case you probably want to use private link cache rather than shared cache.
Except, of course, that DCWRITEDAEMON must be 1 for this mechanism to work at all.
Hello Ray,
Thank you very much for your reply.
We have observed server getting hang when set the value to 1000 in 24 CPU machine. Behaviour was very strange and we were forced to set back the default value.
We appreciate your explanation that the value is influence by the NO.of CPU's on the server. HIgher the number and value can be set to as low as
1.
Thanks once again.
Sanjay Desai / Anupam Singh.