Configuring InfoSphere CDC with shadow tables in HADR environments

Configuring your shadow tables to work in Db2® high availability disaster recovery (HADR) environments involves ensuring that all the required metadata is available to all the standby servers.

Before you begin

  • Ensure that the same version of InfoSphere CDC is installed on all hosts that will be used for HADR.
  • Ensure that you can log in to the access-server-host as cdc-user.
  • Ensure that the following things are identical on the primary and all standby servers:
    • Db2 instance name
    • Database name
    • TCP/IP port name (svcename)
    • InfoSphere CDC user id, group id, and password
    • Db2 instance owner user and password
    • InfoSphere CDC log location
    • Db2 logarchmeth1 configuration parameters
    • InfoSphere® CDC installation directory ($CDC_HOME)
    • InfoSphere CDC user primary group on each HADR server must be the same primary group as the Db2 instance owner.

About this task


Restrictions

  • If you re-create table mappings, perhaps because of DDL changes to the source row-tables or target shadow tables breaking the original table mapping, the mapping changes are not replicated to the standby servers. You must re-create these table mappings in the standby servers through a separate process.

Procedure

To configure your shadow tables in HADR environments:

  1. Set the InfoSphere CDC users umask to 002 or 007 in the cdc-user-home-dir/.bashrc file to control the default mode bits of new directories and files.
    A setting of 007 restricts anyone other than the InfoSphere CDC user group and members of the Db2 administrator group from accessing the load images that are saved in the refresh loader back up path. A setting of 002 allows users from outside those groups to read the images, but not to modify them.
    The following example shows the umask command added to the .bashrc file: 
    #UMASK ADDED TO ALLOW DB2 USER access CDC_REFRESH_LOADER_BACKUP_PATH
umask 007
  2. Log in to the access-server-host as cdc-user.
  3. Create the access-server-user user with the following properties:
    • The role is SYSADMIN.
    • The user is a manager.
    • The password does not change at first login.
    • The password never expires.
    To create access-server-user, issue the dmcreateuser command as follows:
    cd access-server-installation-dir/bin
./dmcreateuser access-server-user
     access-server-user-fullname
     access-server-user-desc
     access-server-user-password
     SYSADMIN TRUE FALSE TRUE
    For more information about the parameters, see access-server-user
  4. On the HADR primary server, set up the InfoSphere CDC instance for shadow tables. For more information, see Setting up the InfoSphere CDC instance for shadow tables
  5. On the standby servers, ensure that the cdc-refresh-loader-path exists and that it is the same file system path that you specified in step 4. The refresh loader path must be a shared path across all HADR servers. This shared path can be a mount point for a shared volume such as clustered shared disk or NFS.
  6. Use the dmset command to change the InfoSphere CDC refresh behavior to use recoverable load operations. 
    dmset -I cdc-instance-name refresh_loader_with_backup_copy=true 
dmset -I cdc-instance-name refresh_loader_cleanup_backup_copy=false 
dmset -I cdc-instance-name refresh_loader_backup_path=cdc-refresh-loader-backup-path
    These three CDC system parameters enable the following behaviors:
    • The fast loader refresh behavior is changed to enable the COPY YES option for the load operation. A LOAD command that specifies COPY YES allows you to have logs rolled forward on the standby and avoid placing the table space containing the table into backup pending state.
    • The load image is saved into the location specified by refresh_loader_backup_path. The refresh loader backup path that you specify must exist and meet the specified conditions.
  7. Start the 64-bit cdc-instance-name.
    :
    nohup ./dmts64 -I cdc-instance-name &
  8. Verify that cdc-instance-name has the appropriate settings for the system parameters. 
    dmset -I cdc-instance-name
  9. Set up a datastore in one of the following ways: