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Create an HA RDQM

You use the crtmqm command to create a high availability replicated data queue manager (RDQM).


About this task

We can create a high availability replicated data queue manager (RDQM) as a user in the mqm group if the mqm user can use sudo. If the user can also SSH to each node without a password, then you only need run the create RDQM command on one node to create the RDQM on all three nodes. Otherwise we must be root to create an RDQM, and we must run commands on all three nodes.


Procedure

  • To create an RDQM as a user in the mqm group:
    1. Ensure that the mqm user can use sudo to run commands and can connect to each server using SSH without a password.
    2. Enter the following command:
      crtmqm -sx [-fs FilesystemSize] qmname
      where qmname is the name of the replicated data queue manager. We can optionally specify the file system size for the queue manager (that is, the size of the logical volume which is created in the drbdpool volume group).

      The command attempts to use SSH to connect to the other nodes in the cluster as the mqm user. If connection is successful, the secondary instances of the queue manager are created on the nodes. Otherwise, create the secondary instances and then run the crtmqm -sx command (as described for user root).

  • To create an RDQM as user root:
    1. Enter the following command on each of the nodes that are to host secondary instances of the RDQM:
      crtmqm -sxs [-fs FilesystemSize] qmname
      where qmname is the name of the replicated data queue manager. We can optionally specify the file system size for the queue manager (that is, the size of the logical volume which is created in the drbdpool volume group). We must specify the same file system size for the RDQM on all three nodes in the HA group.

      The command creates a secondary instance of the RDQM.

    2. On the remaining node, enter the following command:
      crtmqm -sx [-fs FilesystemSize] qmname
      where qmname is the name of the replicated data queue manager. We can optionally specify the file system size for the queue manager.

      The command determines if the secondary instance of the queue manager exist on the other two nodes. If secondaries exist, the command creates and starts the primary queue manager. If the secondaries do not exist, we are instructed to run the crtmqm -sxs command on each of the nodes.

    Apart from the DataPath (-md) and LogPath (-ld) arguments, all arguments that are valid for creating a standard Linux queue manager are also valid for a primary replicated data queue manager.

    Note: When creating an RDQM, the next free port number above 7000 is allocated for the replication link. If it is discovered that the chosen port is used by another application, the crtmqm command fails with the AMQ6543 error and that port is added to an exclude list. We must delete the secondary instances of the queue manager, then run the crtmqm command again.

  • Delete an HA RDQM
    You use the dltmqm command to delete a high availability replicated data queue manager (RDQM).
  • Migrating a queue manager to become an HA RDQM queue manager
    We can migrate an existing queue manager to become a high availability (HA) replicated data queue manager (RDQM) by backing up its persistent data, then restoring the data to a newly created RDQM queue manager that has the same name.
  • Resizing the filesystem for an HA RDQM queue manager
    To resize the filesystem for an existing high availability (HA) replicated data queue manager (RDQM) you back up its persistent data, then restore the data to a newly created RDQM queue manager that has the same name but a filesystem of a different size.
  • Storing persistent application status
    We can store persistent status information relating to applications along with other queue manager data.

Parent topic: RDQM high availability


Related information

Last updated: 2020-10-04