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DB2 Load - NUMRECS


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Nileshkul

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Joined: 09 May 2016
Posts: 30
Location: India

PostPosted: Sun May 01, 2022 1:38 am
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Is accurate estimation of NUMRECS matter in CPU/Elapsed time for DB2 LOAD. The difference in variance of estimation is more than 30% - e.g. loading 130 rows but NUMRECS given as 200. Will it matter - OR if I provide estimation as 150, will it load data any faster? The numbers 200/130 are just for example, actual numbers are much more in millions, the question is more about if accurate estimation of NUMRECS matters?
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dneufarth

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Joined: 27 Apr 2005
Posts: 387
Location: Inside the SPEW (Cincinnati OH USA)

PostPosted: Sun May 01, 2022 4:21 am
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Code:
NUMRECS
Indicates the number of input records for the specified table or table partition.
integer
A positive integer that is used as an estimate of the number of complete input records that are to be loaded into the specified table. The specified number refers to fully assembled input records when CONTINUEIF is used.
Use the NUMRECS keyword for multi-table table spaces to indicate the number of input records that will be loaded into each of the tables or table partitions.

Specifying the number of records improves the sizing of the sort work data sets that the utility requires when indexes are built in parallel. If the LOAD utility underestimates the size of the sort work data sets, the execution of the LOAD utility could fail.

You can also use the NUMRECS keyword when the input data set is located on tape or if only a fraction of the input records will be loaded.

If an integer value is specified on the SORTKEYS keyword at the table-space level, the NUMRECS keyword cannot be specified in the same LOAD statement.

If multiple tables or partitions are loaded in the same LOAD statement, the NUMRECS keyword must be specified either for all of the tables or partitions or for none of the tables or partitions.


www.ibm.com/docs/en/db2-for-zos/12?topic=load-syntax-options-control-statement
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Nileshkul

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Joined: 09 May 2016
Posts: 30
Location: India

PostPosted: Mon May 02, 2022 6:06 am
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Thanks - so it looks like NUMRECS is just for ensuring memory availability for sorting the records for DB2 LOAD and it will not matter or impact if NUMRECS estimation is much more than actual LOAD record count. Hope I am correct with my understanding.
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Rohit Umarjikar

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Joined: 21 Sep 2010
Posts: 2944
Location: NYC,USA

PostPosted: Thu May 05, 2022 6:48 am
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Pls avoid duplicate posts
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