Modifying the critical mode setting

Complete this task to enable the critical mode setting to prevent writes to source volumes if data cannot be copied to the target volume of the volume pair because of a permanent error.

The critical mode setting is used to determine the behavior of remote mirror and copy (PPRC) pairs or consistency groups after the source and target storage units can no longer communicate or when paths between a volume pair in the specified LSS are lost. This setting is associated with the volume pairs in the LSSs that you selected. This option is available for z/OS environments only.

When you enable the critical mode setting, the volume pair is suspended and further writes to the source volume are not accepted if data cannot be sent to the target volume. The volume pair remains in a suspended state until you correct the problem and either issue a request to resynchronize the volume pair or delete it.

If you do not enable this setting and an error occurs to target volume, the remote mirror and copy feature, suspends the copy pair, allowing subsequent write operations to be copied to the source volume of that volume pair. The storage unit records all tracks that have changed. When the problem is resolved, you can resynchronize the volume pair.

Perform the following steps to modify the critical mode setting:

In the navigation, select Real-time Manager > Copy Services > Paths.
On the Paths — Main page, select LSS copy options from the Select Action drop-down list. Then click Go. The LSS copy options page is displayed.
From the LSS copy options page, accept or modify the storage complex from the Storage complex drop-down list.
Accept or modify the storage unit from the Storage unit drop-down list.
Accept or modify the selected LSSs from the Select LSS drop-down list. The LSSs that you selected appear in the table. If you select All LSSs, the timeout value applies to all LSSs in the storage unit that you selected on this page.
Select the Critical Mode option to enable the setting.
Click OK.
If the attributes and values are not correct, click Cancel as appropriate to return to the page where you want to make changes and then specify the correct values. Otherwise, click OK.