Types of access

Every SMP/E command needs access to the global zone. Some commands also require access to one or more other zones. In addition, commands may need different types of access. For example, LIST only reads data and can, therefore, share it with other LIST jobs. On the other hand, APPLY actually updates the target zone, and, therefore, needs exclusive use of that data set to ensure data set integrity.

To meet the needs of all the commands, SMP/E supports three types of access:

Read access with no control of the zone
This access is required primarily during initialization for each command. For example, SMP/E might check the ZONEINDEX entries in the global zone to obtain the data set name for the target zone for the APPLY command. With this type of access, however, the data in the zone can be changed while SMP/E is checking it.

For this type of access no enqueue is issued. It is, therefore, called read without enqueue.
Read access with shared control of the zone
This access is required during certain phases of processing to ensure that the data being checked is not being changed by another command. For example, when selecting SYSMODs to be applied, SMP/E must ensure that SYSMODs are not being received or rejected at the same time.

To gain this type of access, SMP/E issues a shared enqueue on the data set where the zone resides. This type of access is called read with shared enqueue.
Update access with exclusive control of the zone
This access is required when the zone may be updated during command processing (as the target zone is during APPLY).

To gain this type of access, SMP/E issues an exclusive enqueue on the data set where the zone resides.

This type of access is called update with exclusive enqueue.