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Message Posted: Sun, 10 Aug 2003 @ 20:29:21 GMT

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Subj:   Hash Join Usage
From:   Thomas F. Stanek

I'm looking for some feedback on experiences with Hash Joins, particularly with V2R4.x, although any V2R5 experiences would also by welcome.

I have worked with several clients in the past and in almost all cases, the Hash Join feature has been disabled (HTMemAlloc set to 0). In the past, I have seen some queries that used a Hash Join strategy perform significantly slower in some cases and I know there were at least a few DRs opened in the last 12 months to address Hash Join problems. (Tech Alert NTA 532, 12/3/2002, Tech Alert 569, 10/3/2002)

I'd like to here feedback from anyone who has this feature enabled and, if you are having success with it, what is your HTMemAlloc setting and also your total memory per node. Finally, I'd like to know if your system is being heavily utilized, since the documentation seems to suggest pretty strongly that settings higher than 1% should only be done on lightly used systems.

The questions are being raised because I am currently working with a client that has the HTMemAlloc setting at 5% on a heavily utilized system.

Thanks in advance for any input!


Thomas F. Stanek
TFS Consulting, Inc.


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