When a node failure occurs, a failover will
occur. When sequencing of CRGs occurs, all device CRGs fail over first, then
all data CRGs and lastly application CRGs. For peer CRG, there is no sequence
order, but each node is notified when a failure occurs.
You can verify that the cluster resource group has completed
failover or switchover by checking the status of the CRG.
You can also use blocking to hold the application until the data is available to be processed. While the data-resilient cluster resource groups are being processed, you may want to block access to the data represented by the data CRG. You can block access by using the Block EDRS Access (QxdaBlockEDRS) API and the Check EDRS Block Status (QxdaCheckEDRSBlock) API. If a failover or switchover should occur, you can block and unblock access from within the cluster resource group exit program using these APIs.