Controlling z/OS UNIX System Services (USS/OpenEdition) Support

z/OS has introduced major changes and enhancements to the UNIX for z/OS (OpenEdition) environment to make it part of the MVS core. Consequently, certain applications, such as IBM FTP, were converted to use the USS (Unix Services for z/OS). As a result, IBM FTP stopped issuing allocation and deallocation messages to the JESYSMSG spool dataset.

CMEM provides a special interface to support dataset-triggering events originating from UNIX.

The Unix for z/OS interface is shared by all CMEM installations in the LPAR and is version-independent. The first CMEM subsystem to initialize loads the Unix for z/OS interface module to common storage. This interface is later used by all other CMEM subsystems. Upon startup, every CMEM subsystem registers itself with the Unix for z/OS interface. This registration mechanism enables the Unix for z/OS interface to recognize all the available CMEM subsystems and to call them when a new process is created by a fork/spawn request and associated with a BPXAS initiator (for example, when a new ftp session has started). The CMEM monitors are called one by one in the order that they registered with the interface. The first CMEM subsystem to have a matching rule for this address space will monitor it for z/OS dataset-triggering events.

When a CMEM subsystem shuts down, it removes itself from the Unix for z/OS interface. The last CMEM subsystem to shut down removes the Unix for z/OS interface from common storage.

The following sequences of messages indicate that the Unix for z/OS interface was successfully installed:

• For the first CMEM subsystem to initialize

• For any subsequent CMEM subsystem

The following sequences of messages indicate that the Unix for z/OS interface was successfully deactivated:

• For any CMEM subsystem except from the last subsystem to shut down

• For the last CMEM subsystem to shut down

• CMEM enables the operator to start and stop the Unix for z/OS interface using the Modify operator command. Usually, there is no need to intervene with the default processing performed by CMEM. The following operator commands are available:

F CONTROLO,STARTOE
F,CONTROLO,STOPOE[,FORCE]

• The STARTOE command instructs a CMEM subsystem to restart the Unix for z/OS interface. This includes initializing the interface (if no other subsystem has initialized it) and/or registering the current subsystem with the Unix for z/OS interface. If the STARTOE command is issued for a subsystem that is already registered with the Unix for z/OS interface, the following message is generated:

CME828I SUBSYSTEM ALREADY REGISTERED WITH OPENEDITION INTERFACE

• The STOPOE command instructs a CMEM subsystem to deactivate the Unix for z/OS interface. This includes removing the current subsystem from the Unix for z/OS interface and removing the Unix for z/OS interface from common storage if no other subsystem is using it. If the STOPOE command is issued for a subsystem that is not registered with the Unix for z/OS interface, the following message is generated:

MTO796W SUBSYSTEM NOT REMOVED FROM OPENEDITION INTERFACE: SUBSYSTEM NOT FOUND

• If the STOPOE command is issued when the Unix for z/OS interface is not installed, the following message is issued:

MTO795W OPENEDITION INTERFACE MODULE NOT INSTALLED

• The STOPOE,FORCE command instructs CMEM to remove the Unix for z/OS interface from common storage even if one or more CMEM subsystems are still registered with it.

CMEM also provides Started Procedure CTOOEDSC. This procedure can be started from the console using the START command. Procedure CTOOEDSC acts like a STOPOE,FORCE command and removes the Unix for z/OS interface regardless of any registered subsystems. The STOPOE,FORCE command and procedure CTOOEDSC must be used only in case of emergency.