HP StorageWorks External Storage XP user guide (T1706-96006, June 2006)

34 Preparing for External Storage XP operations
• The local array does not force the external array to reserve the mapped external LU. Therefore, do not
write directly to an external array LU (that is, without writing via the local XP array) with IO Suppression
mode set to Disable from the external array side.
If Flex Copy XP operations are in progress for a volume with IO Suppression mode set to Enable, be
careful when updating data in that external LU from the external array side.
• IO Suppression mode is automatically set to the same status for all LDEVs in a given external LU.
• Cache Mode is automatically set to the same status for all LDEVs in a given external LU.
• If you set an open-system emulation type (such as OPEN-V) when mapping the external LU, you can
use the external LU immediately.
To optionally initialize the LU’s data area, use Volume Manager to format the LU. For instructions, see
the HP StorageWorks LUN Configuration and Security Manager XP user guide for the
XP12000/XP10000/SVS200.
• If you set a mainframe-system emulation type (such as 3390-3) when mapping the external LU, format
the LU or perform the Write to Control Blocks operation to make the volume usable.
After the mapping operation, the mapped LU’s status is Blockade. Use Volume Manager to format the
volume or perform the Write to Control Blocks operation to make the volume usable.
• If you mapped a volume that has already been zero-formatted on the external array side, perform
the Write to Control Blocks operation.
• If you mapped a volume that has not been zero-formatted on the external array side, format the
volume on the local array side.
For instructions on the formatting and Write to Control Blocks operations, see the HP StorageWorks
LUN Configuration and Security Manager XP user guide for the XP12000/XP10000/SVS200.
If you format the external array’s mapped LU from the external array side, data that existed prior to
formatting cannot be ensured. When using the mapped external LU from the mainframe OS, format the
mapped volume from the local array side.
• If you set a mainframe-system emulation type for the mapped LU, host I/O is always propagated
asynchronously to the external LU regardless of the Cache Mode setting.
• External LU attributes (IO Suppression mode and Cache Mode) set when the LU is mapped cannot be
changed while the LU is mapped. To change these attributes, delete the external LU mapping (Delete LU
operation), and remap the LU with different attributes (Add LU operation).
• External LU attributes for all LDEVs created in an external LU are set to the same values. Those attributes
are modified when the LDEVs are reconfigured using Volume Manager.
• Mapped LUs that have different external LU attributes or reside on different arrays cannot be used to
create one LUSE volume.
• A mapped external LU with IO Suppression mode set to Enable (such as for Flex Copy XP) cannot be
used for the local array’s Cache LUN XP operations.
• For a mapped external LU with IO Suppression mode set to Disable (such as for External Storage XP),
Cache LUN XP’s Bind mode is not available.
• If you use the mapped external LU for Cache LUN XP operations and set the bind mode, Cache LUN XP
operations require a cache of twice the capacity of the user data.
• For External Storage XP, IO Suppression mode is typically set to Disable. You cannot use a mapped
external LU with IO Suppression mode set to Enable for pair copy operations in Continuous Access XP,
TrueCopy for z/OS®, Continuous Access XP Journal, Universal Replicator for z/OS, Business Copy XP,
ShadowImage for z/OS, or Snapshot XP. Also, the external LU cannot be used for automatic Auto LUN
XP operations.
• Attributes originally set for an external LU on the external array side (such as port security, LUN
security, and Volume Retention Manager attributes) are not kept when the external LU is mapped as a
local array internal LDEV. To keep the original attributes, set those attributes on the mapped external LU
from the local array side.
• If you mapped the external LU and previously set the VMA of LUN Security XP Extension in that volume,
the former VMA setting is superseded when you map the volume again. However, if LUN Security XP
Extension is not installed when you remap the volume, the volume with the VMA setting cannot be
mapped. To change the VMA setting, change it from the local array side.