Interoperability Restrictions For Cache Residency; Cautions And Restrictions For Prestaging - HPE XP7 User Manual

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Remote command device. You cannot allocate the remote command device for Cache
Residency. For more information about the remote command device, see the XP7
External Storage for Open and Mainframe Systems User Guide.
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FlashCopy SE TSE-VOLs. Cache Residency cannot be assigned to a TSE-VOL of
Compatible FlashCopy SE.
Host I/O response time
Performing Cache Residency operations on many LDEVs during host I/O may slow the host
I/O response time. To avoid degradation of response time, set only one LDEV at a time.
Deleting data from cache during host I/O may cause the response time of host I/O to become
slow. To avoid degradation of host response time, limit the amount of data you delete in one
operation as follows:
If the host timeout period is set to 10 seconds or shorter, limit the total amount of data to:
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1 GB or less for open systems
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1,000 cylinders or less for mainframe systems
If the host timeout period is set to 11 seconds or longer, limit the total amount of data to:
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3 GB or less for open systems
◦
3,000 cylinders or less for mainframe systems
Minimum cache requirements
If the remaining cache memory after the cache residency operation will be less than 512
MB, Cache Residency is not available.

Interoperability restrictions for cache residency

Application
Business Copy/ Business
Copy MF
Auto LUN
External Storage

Cautions and restrictions for prestaging

Unsupported volumes
The prestaging function cannot be used for the following volumes:
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Thin Provisioning volume
◦
Thin Provisioning MF volume
Behaviors
Do not perform the Business Copy or Business Copy MF Quick Restore operation
on a Cache Residency volume. Also, do not specify the Cache Residency setting
on the volume on which the Business Copy or Business Copy MF Quick Restore
operation is performed. This operation swaps the internal locations of the source
and target volumes, which causes a loss of data integrity. For additional information,
see the XP7 Business Copy User Guide or XP7 Business Copy for Mainframe
Systems User Guide.
Do not perform the Auto LUN V2 operation on a Cache Residency volume. Also, do
not specify the Cache Residency setting on the volume on which the Auto LUN V2
operation is performed. This operation swaps the internal locations of the source
and target volumes, which causes a loss of data integrity. For additional information,
see the XP7 Auto LUN User Guide and/or contact HPE technical support.
The Cache Residency bind mode is not available to external volumes whose Cache
mode is set to Disable (which is the mode that disables the use of the cache when
there is an I/O request from the host).
Cautions and restrictions for Cache Residency 145