How do I calculate the size for the SYSIDMS parameter SORTSIZE_ESTIMATE when running IDMSDBAN?

Document ID : KB000015659
Last Modified Date : 14/02/2018
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Introduction:

By default IDMSDBAN passes to the SORT a value of 999999999 records. For smaller databases this value is much larger than is required and leads to inefficient use of the sort work space. For larger databases 999999999 may not be enough.

The  SYSIDMS SORTSIZE_ESTIMATE parameter was introduced by PTF RO76079 for 18.0, RO73561 for 18.5 and RO79159 for 19.0 and allows you to specify a more suitable value. Also with PTF RO97151 for 19.0 and RO97147 for 18.5 you can now specify up to 12 digits.

 

Question:

How do I calculate the size for the SYSIDMS parameter SORTSIZE_ESTIMATE?

Answer:

There is no formula to calculate this value.

With IBM and other SORT packages, when you run it, messages are issued to indicate the number of records read.  Use these sort statistics from previous runs to set the SORTSIZE_ESTIMATE value for future runs. 

For small  databases, start with a smaller number for SORTSIZE_ESTIMATE than 999999999 and then compare to the number of sort records read. If lower than the sort records read then you should increase the value. 

For large databases, start with a number larger than 999999999 and then compare to the number of sort records read. If lower than the sort records read then you should increase the value.