The CVAFDIR macro can be used to read or write one or more DSCBs and is described in CVAFDIR Macro Overview and Specification. After a CVAFDIR call, you can test the CV1IVT bit in the CVPL to determine whether the VTOC is indexed or nonindexed.

If the first buffer is 96 bytes, CVAF issues a channel program to verify that the key in the DSCB matches the 44-byte data set name you entered, unless the operation is a write and the BFLENOVR bit is on.

If the first buffer is for a 96-byte write and the BFLENOVR bit in the BFLEFL is set to 1, CVAF skips the key verification, improving performance. If you are not certain that the data set name you provide is correct, set the BFLENOVR bit to 0. If the BFLENOVR bit is set to 0, CVAF does not execute the write unless the keys match.

If CVAF is performing key verification, and the DSCB key does not match the data set name you supply, CVAF ignores any specified BFLEARG and writes the first DSCB using the rules described in the following section, Specifying a Data Set Name to Read or Write a DSCB.