Testing the Contents of ACB, EXLST, and RPL Fields

With the TESTCB macro, VSAM compares the contents of a field you specify with a value that you specify. To show the result of this comparison, VSAM sets the condition code in the PSW (program status word). Only one keyword can be specified each time TESTCB is issued. Use TESTCB to find out:

If an action has been done by VSAM or your program (for example, opening a data set or activating an exit).
What kind of a data set is being processed to alter your program logic as a result of the test.

After issuing a TESTCB macro, examine the PSW condition code. If the TESTCB is not successful, register 15 contains an error code and VSAM passes control to an error routine, if one has been specified. For a keyword specified as an option or a name, you test for an equal or unequal comparison; for a keyword specified as an address or a number, you test for an equal, unequal, high, low, not-high, or not-low condition.

VSAM compares A to B, where A is the contents of the field and B is the value to compare. A low condition means, for example, A is lower than B — that is, the value in the control block is lower than the value you specified. If you specify a list of option codes for a keyword (for example, MACRF=(ADR,DIR)), each of them must equal the corresponding value in the control block for you to get an equal condition.

Some of the fields can be tested at any time; others, only after a data set is opened. The ones that can be tested only after a data set is opened can, for a key-sequenced data set, pertain either to the data or to the index, as specified in the OBJECT parameter.

You can display fields using the SHOWCB macro at the same time you test the fields.