Shared tables: Virtual Table Share (VTS)

Significant reduction of virtual storage utilization is possible when accessing tables from a VTS-TSR. If your installation uses multiple IMS regions or multiple CICS regions that each require access to the same tables, without VTS the tables are replicated in the TSR local to each region. Since each IMS or CICS region can access tables from a common VTS-TSR, the storage required for local TSRs can be greatly reduced or eliminated altogether. If a local TSR is not required after moving all the tables into a VTS-TSR, the local TSR size can be reduced to the absolute minimum by setting the TSRSIZE=0. For more information, see the TSRSIZE parameter description in Appendix A of the tableBASE Installation Guide.

If multiple users could be updating a table—whether online, in a VTS-TSR or other multitasking environment—be aware that a LOCK-LATCH is available to restrict updates to authorized users/applications. It is not required.

In a read/write VTS environment, it is important to ensure all tableBASE jobs operate at the same WLM priority level. This is to insure that a low priority job does not lock out a high priority job. This can occur when the low priority job is updating a tableBASE table and is interrupted by MVS.