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CMS DSN Considerations

If you are using CMS file‑level protection, CA ACF2 for VM performs at least two validations. One when a user LINKs a minidisk against a VM minidisk rule entry, and the other when the user opens a file or performs the first I/O operation against a file.

The net result is that you have combined rules and separate rules depending on the type of files being accessed. For example, consider a user requesting access to the following data:

VSAM Files: TAX.MASTER.INDEX on PAYROLL 0201 minidisk
      TAX.MASTER.DATA on PAYROLL 0202 minidisk
 
CMS Files: CALCTAX MODULE on PAYROLL 0192 minidisk
      TAX   TABLE on PAYROLL 0193 minidisk

First, LINK to the minidisks. The LINK commands then generate the following DSNs:

PAYROLL.V0201.VOLUME
PAYROLL.V0202.VOLUME
PAYROLL.V0192.VOLUME
PAYROLL.V0193.VOLUME

If the files were opened or an I/O operation occurred against them,
CA ACF2 for VM generates the following DSNs:

TAX.MASTER.INDEX
TAX.MASTER.DATA
PAYROLL.V0192.CALCTAX.MODULE
PAYROLL.V0193.TAX.TABLE

Taking the above DSNs and assuming that you did not use masking, your rules need to have the following DSNs:

$KEY(PAYROLL)
 V0192.CALCTAX.MODULE
 V0193.TAX.TABLE
 V0201.VOLUME
 V0202.VOLUME
 V0192.VOLUME
 V0193.VOLUME
 
$KEY(TAX)
 MASTER.INDEX
 MASTER.DATA

The VM minidisk access and CMS file rules are covered in one rule set based on who owns the minidisk. For the VSAM files, there are two rules involved. The PAYROLL rule covers the minidisk access, and the TAX rule covers the VSAM file access. This is because of the need to be compatible with CA ACF2 for VM for OS/390 where typically the high‑level index determines file ownership. A good example is how CA ACF2 for VM for OS/390 generates TSO DSNs based on the logonid as the high‑level index. However, by carefully choosing filenames, you can cover all of the accesses with one rule, for example, if you renamed the TAX.* files to PAYROLL.*.