9 OracleAS Disaster Recovery

This chapter describes issues associated with OracleAS Disaster Recovery. It includes the following topics:

Section 9.1, "General Issues and Workarounds"

9.1 General Issues and Workarounds

This section describes general issues and workarounds. It includes the following topic:

Section 9.1.1, "Adding an Instance from a Remote Client Adds an Instance on the Local Instance and Not on the Remote Instance"
Section 9.1.2, "Switchover Operation in an Asymmetric Topology Requires All Components to be Shutdown on Instances on the Primary Site that Do Not Have a Standby Peer"
Section 9.1.3, "Error "prefix too long" Occurs During Image Backup"

9.1.1 Adding an Instance from a Remote Client Adds an Instance on the Local Instance and Not on the Remote Instance

When using the asgctl add instance command, the OracleAS Guard client must be run from a system that is already included in the topology.

For example, when an OracleAS Guard client is connected to the OracleAS Guard server that is to be added to an existing topology, the following error is returned:

ASG_IAS-15785: ERROR: The topology is missing the instance that exists in the home 
where the ASG server is running. 
You must first discover or add the instance in home

The workaround to this problem is to use an OracleAS Guard client from a system that is already included in the topology to perform the asgctl add instance command to add an instance to the topology.

9.1.2 Switchover Operation in an Asymmetric Topology Requires All Components to be Shutdown on Instances on the Primary Site that Do Not Have a Standby Peer

Prior to performing an asgctl switchover operation in an asymmetric topology for instances that do not have a standby peer, you must perform an opmnctl stopall command to shutdown all components on each of these ignored instances on the primary site.

When an XML policy file is in use for an asymmetric topology and has the <instanceList successRequirement ="Ignore" set for an instance, for example, as shown in the following example, then in a switchover operation OracleAS Guard ignores that instance:

.
.
.
<instanceList successRequirement = "Ignore">
  <instance>instance B</instance>
</instanceList>
.
.
.

OracleAS Guard, on a switchover operation, shuts down all components on the old primary site except for OracleAS Guard and OPMN and ignores instance B because the policy file specifies to do so. The switchover operation fails because all components are not shut down on the primary site, in this case instance B because the policy file specifies to ignore instance B on the primary site, which has no standby peer.

To workaround this problem, the OracleAS Disaster Recovery Administrator must perform an opmnctl stopall operation for all components on instance B prior to the switchover operation in order for the switchover operation to succeed in this asymmetric topology.

9.1.3 Error "prefix too long" Occurs During Image Backup

The following command and option is used to create an image backup during the set of Oracle Application Server backup and recovery operations:

bkp_restore.sh -m node_backup -o image_backup -P

This command uses the first tar executable found in your $PATH. The command may fail with "prefix too long" errors due to long pathname limitations in the /usr/bin/tar executable that is installed by default on HP-UX PARISC systems. The workaround for this issue is to install a tar that does not have long pathname limitations into /usr/local/bin and place /usr/local/bin within $PATH before /usr/bin and before the Image Backup command is executed.