Examples of Off-Host Processing

The examples in this chapter assume that the following VVR configuration has been set up on the Primary and Secondary hosts:

Name of the Primary host: seattle

Name of the Secondary host: london

These examples use the application name dss_app for off-host processing tasks.

Example 1---Decision Support Using the Snapshot Feature and the vradmin ibc Command

1. Create the following directory on both Primary and Secondary hosts:
     /etc/vx/vvr/ibc_scripts/dss_app
2. Create the quiesce and unquiesce scripts and copy them to the /etc/vx/vvr/ibc_scripts/dss_app directory on the Primary host.

   In the quiesce script, provide commands to put the application that is using the Primary data volumes hr_dv01 and hr_dv02 in quiesce mode.

   In the unquiesce script, provide commands to resume the application or take it out of the quiesce mode.

3. Create the prefreeze and onfreeze scripts and copy them to the /etc/vx/vvr/ibc_scripts/dss_app directory on the Secondary host.

   In the prefreeze script, include the following commands to add snapshot plexes to the Secondary data volumes hr_dv01 and hr_dv02:

   
     #!/bin/sh
     /usr/sbin/vxassist –g hrdg snapstart hr_dv01
     /usr/sbin/vxassist –g hrdg snapstart hr_dv02

   In the onfreeze script, include the following command to take the snapshot of the Secondary volumes:

   
     /usr/sbin/vxrvg -g hrdg snapshot hr_rvg

   ---

     Note    This example does not need a postfreeze script.

   ---

4. Run the following vradmin ibc command from any host in the RDS:
     # vradmin –g hrdg ibc hr_rvg dss_app london
5. On the Secondary, use the snapshot data volumes SNAP-hr_dv01 and SNAP-hr_dv02 to run the DSS application, that is, for off-host processing.
6. When the DSS application completes, reattach the snapshot plexes to the data volumes by issuing the following command on the Secondary host london:
     # vxrvg –g hrdg snapback hr_rvg

   The snapback destroys the SNAP volumes and reattaches the snapshot plexes to their original volumes. If you have enabled FR on these volumes, the reattach is faster.

Example 2---Backing Up Using the Snapshot Feature and the vradmin ibc Command

1. Perform step 1 and step 2 from Example 1---Decision Support Using the Snapshot Feature and the vradmin ibc Command.
2. Create the prefreeze, onfreeze, and postfreeze scripts and copy them in the /etc/vx/vvr/ibc_scripts/dss_app directory on the Secondary host.

   In the prefreeze script, include the following commands to add snapshot plexes to the Secondary data volumes hr_dv01 and hr_dv02:

   
      #!/bin/sh
     /usr/sbin/vxassist –g hrdg snapstart hr_dv01
     /usr/sbin/vxassist –g hrdg snapstart hr_dv02

   In the onfreeze script, include the following command to take the snapshot of the Secondary volumes:

   
     /usr/sbin/vxrvg -g hrdg snapshot hr_rvg

   In the postfreeze script, include the following commands to back up the snapshot volumes and to reattach the snapshot plexes to the original volumes after the backup is complete:

   
     # Back up data from SNAP-hr_dv01 and SNAP-hr_dv02
     dd if=/dev/vx/rdsk/hrdg/SNAP-hr_dv01 of=/dev/rmt/0
     dd if=/dev/vx/rdsk/hrdg/SNAP-hr_dv02 of=/dev/rmt/0
     # Reattach the snapshot volumes to the Secondary data volumes
     /usr/sbin/vxrvg -g hrdg snapback hr_rvg
3. Run the following vradmin ibc command from any host in the RDS:
     # vradmin –g hrdg ibc hr_rvg dss_app london

Example 3---Performing Block-Level Backup of the Secondary Data Using the vradmin ibc Command

This method performs the backup directly from the Secondary data volumes while the replication to Secondary is frozen. Make sure the Secondary SRL is large enough to hold the writes sent from the Primary while the backup is in progress. In this method, the Secondary data volumes are under replication control, and hence you cannot write to them. Use this method only if the backup process does not perform any writes to the Secondary data volumes.

1. Perform step 1 and step 2 from Example 1---Decision Support Using the Snapshot Feature and the vradmin ibc Command.
2. Create the onfreeze script and copy it in the /etc/vx/vvr/ibc_scripts/dss_app directory on Secondary host:

   In the onfreeze script, include the following commands to perform block-level backup of the Secondary data volumes:

   
      #!/bin/sh
     dd if=/dev/vx/rdsk/hrdg/hr_dv01 of=/dev/rmt/0
     dd if=/dev/vx/rdsk/hrdg/hr_dv02 of=/dev/rmt/0

   ---

     Note    This example does not need the prefreeze and postfreeze scripts.

   ---

3. Run the following vradmin ibc command from any host in the RDS:
     # vradmin –g hrdg ibc hr_rvg dss_app london