This error might be caused by a problem on the primary system, a problem on the secondary system, or a problem on the intersystem link. The problem might be a failure of a component, a component becoming unavailable or having reduced performance because of a service action or it might be that the performance of a component dropped to a level where the Metro Mirror or Global Mirror relationship cannot be maintained. Alternatively the error might be caused by a change in the performance requirements of the applications using Metro Mirror or Global Mirror.
This error is reported on the primary system when the copy relationship has not progressed sufficiently over a period of time. Therefore, if the relationship is restarted before all of the problems are fixed, the error might be reported again when the time period next expires (the default period is five minutes).
This error might also be reported because the primary system has encountered read errors.
You might need to refer to the Copy Services features information in the software installation and configuration documentation while you diagnose this error.
When you restart the Metro Mirror or Global Mirror relationship there is an initial period during which Metro Mirror or Global Mirror performs a background copy to resynchronize the volume data on the primary and secondary systems. During this period the data on the Metro Mirror or Global Mirror auxiliary volumes on the secondary system is inconsistent and the volumes cannot be used as backup disks by your applications.
Note: To ensure the system has the capacity to handle the background copy load, you might want to delay restarting the Metro Mirror or Global Mirror relationship until there is a quiet period when the secondary system and the SAN fabric (including the intersystem link) have the required capacity. If the required capacity is not available you might experience another 1920 error and the Metro Mirror or Global Mirror relationship will stop in an inconsistent state.
Note: If the Metro Mirror or Global Mirror relationship has stopped in a consistent state ("consistent-stopped") it is possible to use the data on the Metro Mirror or Global Mirror auxiliary volumes on the secondary system as backup disks by your applications. You might therefore want to start a Flash Copy of your Metro Mirror or Global Mirror auxiliary disks on the secondary system before restarting the Metro Mirror or Global Mirror relationship. This means you maintain the current, consistent, image until the time when the Metro Mirror or Global Mirror relationship is again synchronized and in a consistent state.
Possible Cause-FRUs or other:
Other: