Analyzing and validating the consistency group state

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Complete this task to analyze and validate the consistency group state. This is the fourth step in the Global Mirror failover recovery process.

Before you begin

Before you can start this task, you must ensure that the following tasks have been completed:
  • Global Mirror processing has been ended at the primary server site.
  • The status of Global Mirror transaction processing before the disaster caused the process to end has been obtained.
  • Failover processing from B volumes to A volumes has completed with the B volumes state being changed from a secondary, target pending state to a primary, suspended state.

About this task

The consistency group state must be validated. This means that you must investigate whether all FlashCopy® relationships are in a consistent state. Query the FlashCopy relationships that exist between B volumes and C volumes to determine the state of the FlashCopy relationship at the time that the primary server experienced a failure. Global Mirror might have been in the middle of forming a consistency group and FlashCopy might not have completed to create a complete set of consistent C volumes.

When you query a FlashCopy pair, there are two key pieces of information, that determine whether the C volume set is consistent or needs intervention to correct some states.
Revertible status
The revertible status is indicated as Enable or Disable and shows whether the FlashCopy is revertible or nonrevertible. A nonrevertible state means that a FlashCopy process has completed successfully and all changes are committed.
Sequence number
The sequence number indicates the number of the actual or last FlashCopy process (if the FlashCopy process is finished).
There are some combinations of revertible states and FlashCopy sequence numbers that require different corrective actions; this is, what you are looking for when you do your analysis.

Complete the following steps to analyze and validate the consistency group state. The example command displayed in this task is shown in two formats. The first format shows the type of information that the command requires. The second format provides the command with declared values for the variables.

Note: You can issue the commands that are described in the steps for a DS8000® model.

Procedure

  1. Issue the lsflash command to provide a report that lists the FlashCopy relationships and status information for each FlashCopy relationship in the list. Enter the lsflash command at the dscli command prompt with the following parameters and variables:

    dscli> lsflash -dev storage_image_ID -l source_volume_ID:target_volume_ID

    Example

    dscli> lsflash -dev IBM.2107-75FA150 -l 0100:0200 0101:0201
0102:0202 0103:0203

    Remember that your remote server has become your primary server.

  2. Analyze your report to determine the state of the consistency group between the B volume and C volume. You are looking primarily at the FlashCopy relationships and your analysis determines your next step in the recovery process.
    The following provides the types of FlashCopy relationships that might exist and a reference to the action that must be taken:
    • The FlashCopy relationships are nonrevertible and all the sequence numbers are equal. Action: No further action is necessary and the set of C volumes is consistent and a complete copy.
    • The FlashCopy relationships are revertible and all the sequence numbers are equal. Action: Issue the revertflash command to revert the FlashCopy pairs to the last consistency group.
    • All the FlashCopy sequence numbers are equal and at least one of the FlashCopy relationships is nonrevertible. Action: Issue the commitflash command to commit the data to a target volume to form a consistency group between the source and target.
    • The FlashCopy relationships appear as follows:
      1. Some of the FlashCopy relationships completed processing so that a consistent group was created. These FlashCopy relationships are no longer revertible.
      2. Some of the FlashCopy relationships have not completed creating a consistency group formation. They are still in a revertible state.
      3. All the FlashCopy relationships have the same FlashCopy sequence number. This indicates that all the FlashCopy relationships were involved in the same consistency group.
      Action: Issue the commitflash command to commit the data of the FlashCopy relationships that have not completed creating a new consistency group so that a consistency group is formed.
    • There is a group of FlashCopy pairs that are all revertible and another group of FlashCopy pairs that are all nonrevertible. In addition, all the FlashCopy sequence numbers are not equal. However, the following conditions exist:
      1. The FlashCopy sequence number for all revertible pairs is equal.
      2. The FlashCopy sequence number for all nonrevertible pairs is equal.
      Action: Issue the revertflash command to revert the FlashCopy pairs to the last consistency group.
    • The FlashCopy sequence numbers are not equal for all FlashCopy relationships in the concerned consistency group and either a or b in the previous bullet was not true. This indicates that the consistency group is corrupted. Action: Contact your service representative.
    Note: When you know the state of all the FlashCopy relationships, you might want to start a tape backup of the C volume.

What to do next

After determining the state of the FlashCopy relationships, issue the revertflash or commitflash commands, as appropriate.