Allocation of FDS - FILES.

Document ID : KB000049802
Last Modified Date : 14/02/2018
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Could we have more information about the allocation of the FILES data set.


The FILEINIT creates indices and data blocks for all defined sub files.

The number supplied in the FILEDEFN member entry is the maximum number of indexable records, not the physical capacity of the FDS. That depends on how many cylinders allocated to the FDS.

If the client knows how many records he wants and he must also calculate how much physical space is required.

Please refer to CA DISK r12.5 Systems guide, chapter 2 "Files Data Set Management" > FDS Capacity > Estimating Physical Space Requirements.

On page 39 it shows:

Total number of tracks = (Subfile Capacity Requirements)/(Records per Track)

For example, DSNINDEX length is 256 number of bytes per track is 55,996.

So, the number of records per track is 218

If client wants to allocate 1 million records for DSNINDEX, then 1000000/218/15 need 305 cylinders.

Click this link to download a FILES data set Tutorial.

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