z/VM: CP Commands and Utilities Reference - z/VM - IBM

If the START command is issued when no virtual machine is connected with an
active path to *MONITOR for event data, event recording is held pending until
there is a connection with an active path.
3. The event configuration message may be delayed for a user who connects to
*MONITOR to collect event data and, in turn, the event data notification
messages are also delayed for the user.
v If another user has already connected to *MONITOR to collect event data
and has not replied to the event configuration message, the monitor
regenerates the configuration records after the configuration area has been
freed, and sends an event configuration message to the user who has just
connected to *MONITOR
v If a user’s path is quiesced (or at its IUCV message limit) when the event
configuration notification is sent, the user receives notification for a refreshed
set of configuration records when he or she resumes the path to *MONITOR
(or responds to one or more previous messages).
4. The event profile can be changed after monitoring has started. The only
exceptions are that the partition size and the event config size of the saved
segment cannot be changed unless event monitoring is stopped. New event
domains are activated upon completion of the event command.
5. Event monitoring can result in large volumes of data generated and an
increased CP overhead, particularly in the SEEKS and SCHEDULER domains.
For this reason, these two domains should be enabled only when needed and
should be limited to specific devices or a specific set of devices.
Specific Usage Notes for I/O and SEEKS:
1. Any overlapping of I/O devices can exist in a series of MONITOR EVENT
commands on the I/O domain and the SEEKS domain. For example, a
command:
monitor event enable i/o type 3380
followed by:
monitor event enable i/o class dasd
would result in all DASD’s enabled for monitoring. If this is then followed by:
monitor event disable i/o type 3380
monitoring ceases for all 3380 devices but continues for all other types of DASD
devices.
2. A message is issued for any device that had been specified but does not exist.
For the SEEKS domain, a message is issued for any specified device that is
found not to be a DASD.
3. Devices that are enabled but are found to be offline are monitored after they are
varied online. A summary message is issued indicating how many devices are
enabled for monitoring, and how many are offline.
4. The VOLUME operand can be used only for volumes attached to the system,
because CP associates a volume label to a device number only at the time it is
attached. If you want to enable a DASD device that is not attached to the
system, use the DEVICE option.
5. The volume to be monitored is maintained by its device address. Enabling or
disabling a volume for monitoring remains valid as long as its device address
does not change. For example, if a volume is detached and a volume with the
same label at a different address is attached, the volume must be enabled
again to be monitored and its previous device address disabled.
Specific Usage Notes for BLOCK:
1. If BLOCK is omitted, the default is four 4 KB pages.
2. The minimum value for BLOCK is four 4 KB pages.
MONITOR EVENT
Chapter 2. CP Commands 631