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sqlcode1
Active Member
Joined: 08 Apr 2010
Posts: 577
Location: USA
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Frank,
My comments for not using multiple subsets in this situation was relating to the fact that SUBSET may have to invoke SORT routine twice in performing TRAILER operations. Also the solution which I was referring to OP about ,was provided by you in some other thread and hence I asked OP to seek your feedback/comments.
From DFSort Application Programming
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| If the criteria includes the last n records, ICETOOL may call DFSORT twice. For the first pass, ICETOOL counts the indd records without opening the output data sets. For the second pass, ICETOOL opens the output data sets and does SUBSET processing against the indd data set using the count obtained in the first pass. |
Since this topic went little sidetracked, I decided to share only little information which was relevant.
Thanks, |
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Frank Yaeger
DFSORT Developer
Joined: 15 Feb 2005
Posts: 7129
Location: San Jose, CA
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Yes, it may invoke DFSORT twice, but for two copy operations which is usually pretty fast and in the case of SUBSET, it's a special copy operation which is even faster.
The other solution I gave is actually similar to the SUBSET solution and may or may not perform better. The only way to know would be to try them both with the specific data of interest. But I wouldn't make a blanket statement that one is necessarily more efficient than the other without testing them.
What I'm really trying to say here is: I would advise against making blanket statements about what is more efficient than what. YMMV. |
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