VSAM File Sharing Without CA-L-Serv › How It Works

How It Works

In CA TPX, the VSAM data sets are shared by setting VSAM share options to (4,3). ENQ/DEQ logic manages the sharing process.

The ENQ uses a RESERVE to serialize access to the VSAM data sets. The qname of this ENQ is TPXMS. If the VSAM data set is cataloged in an ICF catalog, the rname is the name of the data set. If the VSAM data set is not cataloged, the rname is the data definition name, ADMIN1, ADMIN2, MAIL, NOTES, or VIEW. Testing has shown that converting the RESERVE using a product such as CA MII is not necessary and increases the overhead associated with the cross-system sharing process.

Important! The overhead associated with this serialization causes considerably higher I/O rates to the VSAM data sets.

Sharing information about each VSAM data set is maintained in record zero of the data set (the key consists of 17 “0”s). The VSAM shared information (VSI) for the Data and Index data sets is written to record zero to pass the information cross-system. If any VSAM data set is restored or moved, the information in control record zero becomes inaccurate, so it must be deleted. You can use batch administration to delete control record zero. For more information, see the Batch Administration Guide.

If a VSAM data set is coded as DISP=SHR in the DD statement in the startup procedure, that data set will be shared.