Reading Sets of DSCBs with CVAF Filter

You can use the CVAFFILT macro to retrieve sets of DSCBs into buffers provided by the calling program. CVAF filter service supports both indexed and nonindexed VTOCs. CVAFFILT Macro Overview and Specification describes the macro's format and parameters. The following section summarizes this service and its requirements.

Request DSCBs by specifying either one or more fully-qualified data set names, or one partially-qualified name. See Filter Criteria List (FCL) and Partially-Qualified Names for CVAFFILT for further information.
Identify a single DASD volume in the CVPL.
For each data set that has a format-1 DSCB, the VTOC order returned by CVAFFILT is the format-1 DSCB, followed by any format 3 DSCBs.
For each data set that has a format-8 DSCB, the VTOC order returned by CVAFFILT is the format-8 DSCB, one or more format-9 DSCBs, followed by any format-3 DSCBs. Currently, the minimum buffer list entry size needed to read all DSCBs associated with a data set is 12. This is one format-8 DSCB, one format-9 DSCB, and 10 format-3 DSCBs to reach the 123-extent limit.
CVAF filter service returns DSCB information for one or more qualifying data sets into caller-provided buffers. See Example of CVAFFILT Macro Sequences and Example of Using the CVAFFILT Macro for further information. CVAF filter service does not return a partial DSCB chain in the following cases:
- If you do not provide enough buffers to hold the requested DSCBs, CVAF filter service returns one or more complete DSCB chains and/or a status code (CVSTAT in the CVPL). The status code indicates if a RESUME CVAF call can be used to retrieve the rest (or more) of the DSCBs. See RESUME Capability for specific information.
- If the total number of buffers is insufficient to contain a data set's complete DSCB chain, CVAF filter service sets the FCLDSNST byte in the FCL, ignores the data set, and processes the next qualifying data set. To avoid this situation, provide a minimum of eleven DSCB buffers (enough for a data set at the 123 extent limit).
For fully qualified data set names in the Filter Criteria List, a CVAFFILT request issued to an extended address volume will fail if the EADSCB=OK indicator is not set and the DSCB associated with the fully qualified data set name is described by a format-8 DSCB. For partially qualified data set names in the Filter Criteria List, a CVAFFILT request issued to an extended address volume will fail if the EADSCB=OK indicator is not set and a DSCB associated with a data set that matches the Filter Criteria List is described by a format- 8 DSCB. In both these cases, the data set name status in the FCL (FCLDSNST) will be set to a status value of (x'06'). This status code indicates that a data set name is described by a format-8 DSCB and the caller did not specify support for it with the EADSCB=OK keyword. It will be set only when other data set name status codes are not applicable. CVAF status code (CVSTAT) of STAT086 (x'56') will be set with these errors. This status code indicates all of the user FCL entries were processed, a resume is not required, one or more errors were found.