ISPF uses RESERVE to protect data sets residing on a shared volume. However, PDSEs are designed to be shared in a sysplex, so Configuration Table keyword PDSE_RESERVE_PROCESSING can be used to disable the use of RESERVE.

Assuming a PDSE is being processed and ISPF services are used to the access the PDSE then:

PDSE_RESERVE_PROCESSING=ON (default)

RESERVE issued prior to STOW and released afterwards. LMOPEN with ENQ(SHRW) issues a RESERVE at LMOPEN and OPTION(OUTPUT). If batch job issues RESERVE before an interactive user, then the interactive user waits on SAVE until the batch dialog releases the RESERVE. Another batch job will also wait. See the description of LMCLOSE in

PDSE_RESERVE_PROCESSING=OFF

No RESERVE is issued. DFSMS preserves the integrity of the PDSE. Interactive users and batch jobs can access the PDSE simultaneously. ISPF dialogs continue to use Member name enqueue to serialize access to individual members. In environments where there may be more than one Configuration Table, the dialog that issues a RESERVE will only wait for another dialog that also issues RESERVE. See SC26-7410 DFSMS Using Data Sets 3.8.9.3.3 Choosing Volumes for PDSEs in a Sysplex.