Administering Replication

VRW enables you to administer Secondary hosts from any host in the RDS. You can perform the following replication tasks using VRW:

• Changing the Replication Settings
• Pausing Replication to a Secondary
• Resuming Replication to a Secondary
• Stopping Replication to a Secondary
• Changing the IP Addresses Used for Replication

The replication tasks are independent of the host from which they are accessed and can be accessed from any host in an RDS. The host on which the task is launched is referred to as the local host. The name of the RVG on the local host represents the RDS name to which it belongs.

Changing the Replication Settings

Use Configuration > Change Replication Settings to change the VVR replication attributes according to your requirements. The Change Replication Settings task enables you to set the following VVR replication attributes:

• Replication mode
• Latency protection
• SRL protection
• Replication protocol
• Bandwidth limit
• Packet size

For details on selecting the appropriate option for each replication attribute, see the VERITAS Volume Replicator Administrator's Guide. Note that the replication settings are applied to both the Primary and the Secondary. For more information on replication settings, see Adding a Secondary to the RDS.

  To change replication settings to a Secondary in an RDS

1. Select the Secondary RVG view of the RDS for which you want to change the replication settings.
2. Choose Configuration > Change Replication Settings.
3. Complete the Change Replication Settings page as follows:

   Replication Mode Asynchronous, Synchronous-Override	The current replication mode is displayed by default. From the drop-down list, select the required mode of replication. To set the replication to synchronous mode, select Synchronous-Override. To set the replication to asynchronous mode, select Asynchronous.
   SRL Protection autodcm, dcm, off, override	From the drop-down list, select the required value to change the SRL protection mode. To enable SRL protection, select autodcm, dcm, or override. To disable SRL protection, select off. If you disable SRL protection, the SRL is allowed to overflow. For details on selecting the fail option, see VERITAS Volume Replicator Administrator's Guide.
   Latency Protection override, off	When you select override the wizard displays the fields Latency Low Mark and Latency High Mark with default values of 9950 and 10000 respectively. To disable latency protection, select off. This does not limit the number of waiting updates in the SRL. To enable latency protection and limit the number of waiting updates in the SRL, select override. For details on selecting the override or fail option, see VERITAS Volume  Replicator Administrator's Guide.
   Latency Low Mark	Displays only if Latency Protection is set to override. Enter the number of writes in the SRL at which the protection must become inactive and writes must succeed.
   Latency High Mark	Displays only if Latency Protection is set to override. Enter the numerical limit above which you do not want the number of updates waiting in the SRL to grow. Must be specified when Latency Protection is set to override.
   Protocol	Displays the current network protocol used for replication. Select the desired protocol from the drop-down list.
   Bandwidth Limit	Enter a value, or the word none. Select the desired units from the drop-down list. The minimum value is 56 kbps.
   Packet Size	The default is 8400 bytes. The minimum value is 1300 bytes and the maximum value is 65464 bytes.

4. Click OK to change the replication settings for the selected Secondary. A message indicates whether the operation succeeded or failed.
5. In the status page, click Close. The Secondary RVG view displays the new replication settings.

Starting Replication to a Secondary

Use Replication > Start to start replication to a Secondary. When you start replication to a Secondary, the data volumes on the Secondary must be synchronized with the data volumes on the Primary. For this reason, the Start Replication task is described in conjunction with the synchronization procedures. For more information, refer to Synchronizing the Secondary and Starting Replication.

Pausing Replication to a Secondary

Use Replication > Pause to pause replication to a specific Secondary in an RDS. The Pause Replication task temporarily pauses replication between the Primary and Secondary. The pause is initiated from the Primary and is independent of the host from which the command is entered. Pausing replication from the Primary enables you to perform administrative tasks, such as making changes to the network connecting two nodes.

During a pause, the Primary continues to log writes to the SRL but does not send the writes to the Secondary. The network session between the Primary and Secondary on behalf of the RLINK is broken. A resume re-establishes the Primary-Secondary network session and enables writes to continue from the point of the pause. If there is volume activity during the pause, synchronous RLINKs are forced to become asynchronous. A previously synchronous RLINK remains asynchronous after the resume until it catches up.

  To pause replication to a Secondary

1. From the Secondary RVG view of the required RDS, choose Replication > Pause.
2. In the Pause Replication dialog box, click OK to pause replication. A message indicates whether the operation succeeded or failed.
3. In the status page, click Close. The Secondary RVG view displays the new replication status.

Resuming Replication to a Secondary

Use Replication > Resume to resume replication between the Primary and a specific paused Secondary in an RDS. After replication resumes, the state of the Primary and Secondary RLINKs changes to CONNECT to indicate that replication has resumed. To check the state of RLINKs, check the RLINK section in the Primary RVG view.

  To resume replication to a Secondary

1. From the Secondary RVG view of the required RDS, choose Replication > Resume.
2. In the Resume Replication Summary page, click OK to resume replication. A message indicates whether the operation succeeded or failed.
3. In the status page, click Close. The Secondary RVG view displays the new replication status.

Stopping Replication to a Secondary

Use Replication > Stop from any host in an RDS to stop replication between the Primary and a specified Secondary.

The Stop Replication task fails if the Primary and Secondary RLINKs are not up to date. The dialog box provides an option to stop replication to a Secondary when the RLINKs are not up to date.

Do not use the Stop Replication task to temporarily stop replication; instead, use Replication > Pause.

  To stop replication to a Secondary

1. From the Secondary RVG view of the required RDS, choose Replication > Stop.
2. Complete the Stop Replication dialog box as follows:

   Option: Stop replication even when the Secondary is not up-to-date.

   Select the checkbox to stop replication to the Secondary when the Secondary is not up-to-date.

3. Click OK to stop replication. A message indicates whether the stop replication operation succeeded or failed.
4. In the status page, click Close. The Secondary RVG view displays the new replication status.

Changing the IP Addresses Used for Replication

Use Configuration > Change IP to change the IP addresses used for replication to a specific Secondary in an RDS.

Prerequisites for changing the IP addresses used for replication:

  The new host names must be configured for proper resolution on both the Primary and Secondary sites.

  The Secondary must be reachable from the Primary either through the previous network, the new network, or both the networks.

  If the previous network is no longer available, the change IP task will fail if you are not currently connected to the Primary host.

  To change the replication IP

1. Select the Secondary host for which you want to change the replication settings in the RDS view.
2. From the Secondary RVG view, select Configuration > Change IP.
3. In the Change IP dialog box, enter a value for a new Primary or a new Secondary, or both. The value can be either a host name or an IP address.
4. Click OK to change the replication IP for the selected Secondary. A message indicates whether the operation succeeded or failed.
5. In the status page, click Close. The RVG view displays the new replication settings.