Options set by using Device Manager - Storage Navigator or Command Control Interface

You can set the following ShadowImage options by using Device Manager - Storage Navigator or Command Control Interface (CCI). For details about how to change system options using CCI, see the Command Control Interface User and Reference Guide.

No.	Option	Description
1	Swap & Freeze	Saves ShadowImage data as is immediately after Quick Restore. Used with the Quick Restore, inhibits the update copy operation after Quick Restore, and the paired S-VOL in PAIR status is not updated and remains unchanged.
2	Host I/O Performance	Gives weight to host I/O responses rather than the copy time of a volume. This option controls SI copy operations and improves host I/O responses. This option suppresses copy operations at any time regardless of workload.
20 21 22	Copy Pace Ext. Slower1 Copy Pace Ext. Slower2 Copy Pace Ext. None	Reducing the copy volume in the PAIR status curbs the influence to the I/O performance of the host server. This option is available to all SI pairs in the PAIR status. The I/O performance of the host server is improved most effectively with Copy Pace Ext. None, followed by Copy Pace Ext. Slower2, and Copy Pace Ext. Slower1. Copy Pace Ext. None takes precedence over Copy Pace Ext. Slower2, and Copy Pace Ext. Slower2 takes precedence over Copy Pace Ext. Slower1. This function is enabled only when the pair status is PAIR. If the pair status is COPY(PD)/COPY, COPY(SP)/COPY, PSUS(SP)/PSUS, COPY(RS)/COPY and COPY(RS-R)/RCPY, this function cannot reduce the impact on the host server's I/O performance.
24	Quick/Steady Split Multiplexing (ShadowImage/ShadowImage for Mainframe)	Accelerates SI pair split. The number of jobs used for concurrent copy processing for each pair is changed from 1 to 24.
25	Reverse Copy Multiplexing (ShadowImage/ShadowImage for Mainframe)	Accelerates resynchronization of SI pairs. The number of jobs used for concurrent copy processing for each pair is changed from 1 to 24.

The Host I/O Performance option suppresses copy processing, and prolongs the copy time. Also, if there is an SIz pair, host I/O responses might not be improved. In this case, enable this option for both SI and SIz.

For details about how to set I/O Performance options using Command Control Interface, see the Command Control Interface User and Reference Guide.

Note the following when you use the Quick/Steady Split Multiplexing (ShadowImage/ShadowImage for Mainframe) and Reverse Copy Multiplexing (ShadowImage/ShadowImage for Mainframe) options:

The increase in copy volume, increases the amount of data to be written to the target volume.

If the parity group (for example, physical disk) performance is less than the pair split or resync performance, the amount of data waiting to be written to cache memory (write pending ratio) may increase until it exceeds 60%, and the copy processing might be placed in the wait state. In such a case, consider the copy order to reduce the number of pairs for which copy processing is executed concurrently for volumes provisioned by the same parity group.

If the number of volumes to be resynchronized or split increases, the maximum number of jobs for pair split or resynchronization that can execute concurrently for a pair decreases. In this case, when you split or resynchronize many pairs concurrently with this option set, the pair split or resynchronization performance might not be changed.

The maximum number of copy operations that can be run concurrently is 128. This number includes initial copying, resynchronization, update copying, and differential data copying. When copy operations other than pair split and resynchronization are running concurrently, if you set this option, the pair split or resynchronization performance might not be changed.

When the Copy Pace Ext. None option is set, copy operation is not performed for the pair in the PAIR status. In this case, the PSUS(SP)/PSUS and COPY(SP)/COPY status during split operation might last longer. If this is a problem, perform either of or both the following actions:

Minimize the time that the pair status is PAIR to avoid lowering the sychronization ratio in the PAIR status.

Use this option to change the status to Copy Pace Ext. Slower1 or Copy Pace Ext. Slower2. If you select either of them, the write response might be larger than the one for Copy Pace Ext. None.

Difference between the Host I/O Performance option and the Copy Pace Ext. options:

The Host I/O Performance option reduces the impact on host I/O by lowering the copy activity when a pair is in COPY(PD)/COPY, PAIR, COPY(SP)/COPY, PSUS(SP)/PSUS, COPY(RS)/COPY or COPY(RS-R)/RCPY status.

The Copy Pace Ext. option reduces the impact on host I/O by lowering the copy activity when the pair is the PAIR status. These options can be set concurrently. If you set both options, you can benefit from both.