HP XP P9000 Provisioning for Mainframe Systems User Guide

You can create a system disk on either a mainframe or an open system. To create a system disk,
you create an LDEV and then designate it as a system disk in the Create LDEVs wizard (see “Creating
an LDEV” (page 41)). The system disk designation prevents other storage system structures from
accessing it. It is not available to hosts, or a command device, pool volume, journal, and so on.
The system disk is part of one parity group. When an LDEV is defined as a system disk, the LDEV
cannot be allocated to a port.
The buffering area capacity for the audit log buffer is: 130 MB, that is 185 cylinders if the track
format is 3380-3 or NF80; 154 cylinders if the track format is 3390. Therefore, before using the
audit log, make sure to prepare the system disk to have at minimum the above mentioned free
capacity in the volume. The size of the system disk could be 1 GB if you want some spare capacity,
or as large as 15 GB to accommodate the amount of system information that could be stored on
it.
If you find you do not need a system disk, you can delete the system disk and convert the volume
to free space (see “Deleting an LDEV (converting to free space)” (page 46)).
System disk rules, restrictions, and guidelines
Rules
• The minimum size of the system disk should be 130 MB in order to accommodate audit log
buffer information.
• When creating the system disk in the mainframe system volumes, assign the LDKC:CU:LDEV
number that is not defined in the host's I/O generation.
• The LDKC:CU:LDEV number assigned to the system disk should be distinguishable from the
one for a normal volume.
• Use the Delete LDEVs function to delete the system disk.
Restrictions
• The system disk cannot be created as a THP-VOL.
• The system disk can be specified as any emulation type except 3390-V.
• A system disk cannot be used for any other function or connected to a port.
• Normal data cannot be stored on the system disk.
• The bind mode of Cache Residency Z must not be set for the system disk.
• I/O cannot be issued from the host of the mainframe system. The device number is seen by
the mainframe volume, but the device response is not operational. If an I/O is issued from a
mainframe system host, a failure is reported as a CC=3 condition.
• The system disk should not be deleted or blocked while it is being used. Delete or block the
system disk when it is not being used.
Guidelines
• Although the system disk can be created in an external volume, it is best to use only internal
volumes.
• Although there can be up to 16 volumes of system disks created throughout the entire storage
system, best practice is to have only one system disk per storage system.
• In a mixed configuration of open and mainframe system volumes in a storage system, it is
best to select open volumes for the system disk.
• If you have more than one system disk on your storage system, and one of them is blocked,
the unblocked system disks may not be usable. In this case, delete the blocked system disk,
and then use the other normal system disks.
Using a system disk 53