PCTI parameter for SPACSECI used with Allocation

When the PCTI parameter is specified with the SPACSECI function, the SPACSECI parameter value is ignored. The first extent will be equal to the original secondary allocation. But after that first extent, the original secondary allocation is increased or decreased by the PCTI value whenever the data set extends on the same volume because SPACSECI does not get control after a volume addition.

PCTIACT=S causes the SPACSECI function to honor the SPACSECI parameter when PCTI is specified. PCTICALC specifies how many times the percentage increase calculation is applied to the secondary extent before becoming constant.

The NVOL selection parameter can be used to control the secondary increases after a volume add occurs.

PCTI processing examples

• The following example increases the secondary allocation by 200 percent of the original secondary on all volumes except the first:

  SET SPACSECI=10 PCTI=200
      INC DSN=/ NVOL > 1

• The following example increases the secondary allocation by 300 percent of the original secondary, beginning after the extent specified on the SPACSECI parameter. The PCTI value is applied three times before becoming constant:

  SET SPACSECI=3   PCTI=300   PCTIACT=S   PCTICALC=3
          INC DSN=/

  A data set allocated with SPACE=(TRK,(1,1)) uses:

  • 1 track for extents 2 and 3
  • 3 tracks for extent 4
  • 9 tracks for extent 5
  • 27 tracks for extents 6 through 16

SPACSECI processing example

A data set is allocated with SPACE=(TRK,(1,1)); the primary extent is one track, and the secondary extent is two tracks.

The SPACSECI rule list sets the extent trigger at the second extent as follows:

Secondary allocation quantity modification occurs after the second extent is allocated (on the third extent).