Lock Management › Controlling Access to Native VSAM Files

Controlling Access to Native VSAM Files

Physical Area Locks Not Set

CA IDMS does not maintain physical area locks for areas that map to native VSAM data sets. Therefore, a combination of SHAREOPTIONS, JCL, and operational procedures is used to control updates of native VSAM data sets by CA IDMS, local transactions, and non-CA IDMS programs.

DEFINE CLUSTER Command

For example, you can prevent concurrent update by specifying the parameter SHAREOPTIONS(2,3) in the DEFINE CLUSTER command during VSAM cluster definition. This parameter permits only one application program to open the data set for update, thereby preventing concurrent update of the data set by two application programs executing in different regions. Within a central version, access to native VSAM files is controlled through the use of logical locks on areas and records just as for CA IDMS database files.

CA IDMS/DB Facilities

You can use CA IDMS facilities to further control access to native VSAM data sets. For example, to protect a data set from being updated, set the status within central version to TRANSIENT RETRIEVAL or RETRIEVAL. In this case, no application program running under the central version can ready the area in update mode.

To ensure read integrity of the area when accessed by transactions executing under a central version, you can use the following procedure when updating the data set using non CA IDMS programs:

1. Vary offline the CA IDMS area that maps to the VSAM data set by means of the DCMT VARY AREA OFFLINE command.
2. Run the job to update the VSAM data set.
3. Vary the area to retrieval access mode using the DCMT VARY AREA RETRIEVAL command, thus making the area once again available under the central version.