You can use a number of MVS and VTAM® commands to control APPC/MVS LUs, schedulers, servers, and TPs. Topics in Operating APPC/MVS describe the effects of these commands on protected conversations, if the effects are different from those on unprotected conversations.

One task related to APPC/MVS operations, however, is worth emphasizing here: When you need to stop an APPC/MVS LU, make sure you first use LUDEL to terminate the LU and quiesce its work. IBM® recommends using LUDEL before using any other method that stops one or more LUs, but its use is even more important when your installation has enabled protected conversations support. Unless you first allow an LU to quiesce its work, thereby allowing active protected conversations to end normally, incomplete units of recovery (URs) might result. If so, the system defers resynchronization processing for these incomplete URs, until the LU is re-activated on the same system. This delay might cause the programs associated with the incomplete URs to hang until the LU is restarted.

In addition, if your installation defines a syncpoint-capable LU as a member of a VTAM generic resource group, and an operator issues the CANCEL APPC command before issuing LUDEL first, the system cannot correctly clean up LU session affinity (associated with VTAM generic resources) and the APPC/MVS log stream. This situation might result in unbalanced workload sessions for LUs in a generic resource group, and incorrect log stream contents, once APPC is restarted.