Changing the copy type of remote-copy relationships and consistency groups

You can change the copy type of both relationships and consistency groups between Metro Mirror and Global Mirror.

The system supports the following types of relationships and consistency groups:

Active-active (for HyperSwap® volumes)
Metro Mirror
Global Mirror without cycling (cycling mode set to None)
Global Mirror with change volumes (cycling mode set to Multiple)

Change volumes can be used in a number of cases with relationships. Active-active relationships and Global Mirror relationships with cycling mode set to Multiple must always be configured with change volumes. Metro Mirror and Global Mirror with cycling mode set to None can optionally be configured with change volumes, which can be used to maintain a consistent secondary image. If necessary, you can change the copy type of a Metro Mirror or Global Mirror remote-copy relationship or consistency group without re-creating the relationship or consistency group with the different type. For example, if the latency of the long-distance link affects host performance, you can change the copy type to Global Mirror to improve host performance over high latency links. For Global Mirror relationships with multiple cycling mode, changes are tracked and copied to intermediate change volumes. The changes are transmitted to the secondary site periodically to lower bandwidth requirements. If you are changing either a Metro Mirror or Global Mirror relationship or consistency group to a Global Mirror with change volumes (cycling mode set to Multiple), you must create change volumes on both the master and auxiliary volumes that are used in the relationship or consistency group.

Note: You cannot change the type of a HyperSwap (active-active) relationship or consistency group.

You can change the copy type by using either the management GUI or the command-line interface. However, before you change the copy type of either a relationship or consistency group, consider the following requirements:

Any relationship or consistency group must be in the stopped state (Inconsistent Stopped, Consistent Stopped, or Idling state).
When you change the type for a consistency group, all relationships within the group also change their copy type.

Use the management GUI to change the copy type

You can use the management GUI to change the copy type of different types of relationships.

To change a single relationship, complete the following steps.
1. Select Copy Services > Remote Copy.
2. Expand Not in a group and right-click the relationship that you want to change and select Edit Relationship.
3. In the Edit Relationship dialog, select either Metro or Global for the new copy type. If you are changing the copy type from a Metro to a Global copy type, you need to specify whether to use cycling mode. Set the value to None if you do not want change volumes that are created for this relationship. Set the value to Multiple to create change volumes for this relationship. With multiple cycling mode, changes are tracked and copied to intermediate change volumes and are transferred to the secondary volume periodically to reduce bandwidth requirements. If you select Multiple for the cycling mode, you can specify the number of seconds between copy cycles for the relationship.
4. Click OK.
To update a consistency group, complete these steps:
1. Select Copy Services > Remote Copy.
2. Right-click the consistency group and select Edit Consistency Group.
3. In the Edit Consistency Group dialog, select either Metro or Global for the new copy type. If you are changing the copy type from a Metro to a Global copy type, you need to specify whether to use cycling mode. Set the value to None if you do not want change volumes that are created for this relationship. Set the value to Multiple to create change volumes for this relationship. With multiple cycling mode, changes are tracked and copied to intermediate change volumes and are transferred to the secondary volume periodically to reduce bandwidth requirements. If you select Multiple for the cycling mode, you can specify the number of seconds between copy cycles for the consistency group. The new copy type and settings apply to all the relationships within the group.
4. Click OK.
To change a relationship or a consistency group that had existing change volumes or to change to a Global Mirror with change volumes, you must change both the master and auxiliary systems. To do so, complete the following steps.
1. On the master system, select Copy Services > Remote Copy in the management GUI, right-click the relationship or consistency group that you changed and select Global Mirror Change Volumes. You can select one of the following options:
  Create New
  
  Select this option if you are changing the copy type from either a Metro Mirror or Global Mirror relationship or consistency group to a Global Mirror with change volumes.
  
  Add Existing
  
  Select this option if the system contains existing change volumes.
  
  Delete
  
  Select this option if you are changing the copy type from a Global Mirror with change volumes to either a Global Mirror without change volumes or a Metro Mirror relationship or consistency group.
2. On the auxiliary system, select Copy Services > Remote Copy in the management GUI, right-click the relationship or consistency group that you changed and select Global Mirror Change Volumes. You can select one of the following options:
  Create New
  
  Select this option if you are changing the copy type from either a Metro Mirror or Global Mirror relationship or consistency group to a Global Mirror with change volumes.
  
  Add Existing
  
  Select this option if the existing change volumes are on the system.
  
  Delete
  
  Select this option if you are changing the copy type from a Global Mirror with change volumes to either a Global Mirror without change volumes or a Metro Mirror relationship or consistency group.

Use the CLI to change the copy type

You can enter CLI commands to change the copy type of a relationship. The command and parameters that you enter vary depending on the type of a relationship.

If you are changing a Metro Mirror relationship to a Global Mirror relationship without cycling mode, enter this command, where rc_rel_name is the name of the relationship that you are changing.
```
chrcrelationship -global -cyclingmode none rc_rel_name
```
If you are changing a Metro Mirror relationship to a Global Mirror relationship with multiple cycling mode, complete these steps:
1. On either the master or auxiliary system, run the following commands. The period value specifies the number of seconds that a cycling mode is completed for the relationship and rc_rel_name is the name of the relationship that you are changing.
```
chrcrelationship -global -cyclingmode multi rc_rel_name 
```
```
chrcrelationship -cycleperiodseconds period rc_rel_name 
```
2. On the master system, run the following command, where master_change_vdisk_name is the name of the change volume that is associated with the master volume.
```
chrcrelationship -masterchange master_change_vdisk_name
```
3. On the auxiliary system, run the following command, where aux_change_vdisk_name is the name of the change volume that is associated with the auxiliary volume.
```
chrcrelationship -auxchange aux_change_vdisk_name
```
If you are changing a Global Mirror relationship to a Metro Mirror relationship, enter the following command, where rc_rel_name is the name of the relationship that you are changing.
```
chrcrelationship -metro rc_rel_name
```
To change the copy type of a consistency group, enter one of the following commands.
- If you are changing a Metro Mirror consistency group to a Global Mirror consistency group without cycling mode, enter this command, where rc_consist_group_name is the name of the consistency group that you are changing. All new settings apply to all the relationships within the group.
```
chrcconsistgrp -global -cyclingmode none rc_consist_group_name
```
- If you are changing a Metro Mirror consistency group to a Global Mirror consistency group with multiple cycling mode, enter this command. The period value is the number of seconds that a cycling mode is completed for the relationship and rc_consist_group_name is the name of the consistency group that you are changing. All new settings apply to all the relationships within the group.
```
chrcconsistgrp -global -cyclingmode multi -cycleperiodseconds period rc_consist_group_name
```
- If you are changing a Global Mirror consistency group to a Metro Mirror consistency group, enter this command, where rc_consist_group_name is the name of the consistency group that you are changing. All new settings apply to all the relationships within the group.
```
chrcconsistgrp  -metro rc_consist_group_name
```