Create Metro Mirror relationship — Select copy options

Introduction

After you select source and target volumes for Metro Mirror relationships, select one or more copy options for the volume pairs.

Menu path

Fields

Select relationship type

The type of relationship that you want to create:

Metro Mirror

The storage unit synchronously mirrors the updates to the target volume in a consistent manner. This means that I/O write completion status is updated after updates are committed to the target storage unit.

Global Copy

The storage unit mirrors data in a nonsynchronous manner, at extended distances, with minimum impact on application performance. This means that I/O completion status is updated after updates are committed to the source storage unit. Updates to the target volume are performed at a later point in time. The original order of the updates is not strictly maintained.

Perform initial copy

The copy process that copies the entire source volume to the target volume. Select this option the first time that you create a Metro Mirror relationship because guarantees that the source and target volume contain the same data. If you do not select this option, data cannot be copied from the source volume to the target volume until the first writes are written to the host system when a Metro Mirror relationship is created.

Permit read access from target

Allows host systems to read from the Metro Mirror target volume. The status of the volume pair must be full-duplex for the host system to read the volume pair.

Note: This option is valid only for open-system environments.

Create relationship even if target is online to a host

Allows a Metro Mirror volume relationship to be created even if the target volume is online to host systems.

Note: This option is enabled only for zSeries^® volumes; otherwise, it is disabled.

Suspend Metro Mirror relationship after initial copy

Suspends the volume pair that was created as a Metro Mirror relationship after the source and target volumes are synchronized.

Note: This option is only valid if you select the Perform initial copy when you create the Metro Mirror relationship.

Enable critical volume mode

Determines how write operations are managed when an error occurs to a volume pair. If a volume pair, with the critical volume mode option enabled, suspends because of a communication failure, write I/O to the source volume is rejected. This allows the source to become write protected. In this way, dependent writes cannot process and cannot be sent to the remote site. The volume pair remains suspended until you correct the problem and either resynchronize the volume pair or delete the volume pair.

Note: The Critical volume mode option is disabled if source and target volume selection are fixed block (FB) volumes or if you selected count key data (CKD) volumes using Global Copy mode with the Perform initial copy option enabled.