Coordinating VSAM data set definitions with share options
When your database access method is VSAM, the declaration of the data set indicates to VSAM what degree of shared access is required.
The SHAREOPTIONS parameter values (in the DFSMS DEFINE CLUSTER keyword) and the type of sharing they specify is shown in the following table.
| SHAREOPTIONS value | Type of sharing |
|---|---|
| (1,3) | No sharing, single updater, or multiple readers |
| (2,3) | Single updater and multiple readers |
| (3,3) | Multiple updaters and multiple readers |
For databases that are to participate in block-level sharing and use the VSAM access method, you must include the SHAREOPTIONS (3,3) parameter when defining the data sets. The RECON data set is also accessed as a KSDS and requires SHAREOPTIONS (3,3).
Related reading: For preparation of DFSMS Access Method Services statements that declare and catalog the share options, see z/OS DFSMS Access Method Services for Catalogs.
When using IRLM, you must define SHARELEVEL=1 VSAM databases to VSAM with the appropriate SHAREOPTIONS required for block-level data sharing. This might require you to make a VSAM definition change.
Tailoring the z/OS system for IRLM
Several other system initialization activities are required for the IRLM component:
- Defining the IRLM as a z/OS® subsystem
- Allowing for IRLM trace output
- Arranging for formatted dump output
- Defining an IRLM for sysplex data sharing
These activities are described in System initialization for IRLM.