Systems that rely on running Web Element Manager on a single server to manage their networks face the possibility of service disruption should the server fail. By using Oracle Clusterware or Symantec Veritas software, it is now possible to create redundant Web Element Manager servers with a primary host server running an active instance of Web Element Manager, and a redundant server in standby mode. This appendix provides information to help you successfully configure redundant instances of Web Element Manager over multiple servers. This appendix works closely with the Installing the WEM Software and the WEM Port and Hardware chapters in this guide.
Important: Oracle Clusterware is supported on the Solaris operating system; however, Veritas is supported on Solaris and RHEL. During the installation process a radio button is provided to choose the required software. Web Element Manager must be installed on a minimum of two Sun Netra™ T5220 servers equipped with the hardware described in the Server Hardware Requirements section of this guide.
Important: Ensure you have installed the latest version of Oracle Solaris software and all appropriate software patches as described in the Operating System Requirements section.IPMP is a feature supported on Oracle Solaris. For more complete configuration information, refer to Configuring IPMP for WEM Server and also to the Oracle product documentation.
This section specifies the configuration changes required when installing WEM in Failover Mode rather than Standalone Mode when following the installation instructions in the Installing the WEM Software chapter. For this release, please use the GUI to perform the installation rather than the command line.
Important: Install and configure Web Element Manager in Failover Mode on both servers before configuring a cluster resource group.The following items are either different from, or prerequisites for, the installation steps defined in the Installing the WEM Software chapter:
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The logical hostname and a floating IP address shared between the two nodes must be configured in /etc/hosts. Ems-Service is used as the logical hostname in the examples in the rest of this appendix.
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Create the global disk path for a shared data directory, for example: /shareddir/ems-share.
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Important: The following options are not set when installing in Failover Mode:|
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WEM Service started by default and monitored by Process Monitor. (See the WEM Process Monitor chapter for more information on processes.)
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Important: This process is configured on only one server in the cluster. It is reflected on both. Before clsetup can create a network resource for any logical hostname, that hostname and a common floating IP address associated with it must be specified in the /etc/hosts directory on both servers. This example uses ems-service as the logical hostname.
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Step 1
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Step 2
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From the Main Menu select Option 2: Resource Groups.
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Step 3
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From the Resource Groups Menu, select Option 1: Create a Resource Group.
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Step 4
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When prompted to create a failover group, enter yes and select Option 1: Create a Failover Group. For this example, call the group ems-rg.
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Step 5
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When you are prompted to select a preferred server enter yes and enter the name of the Preferred server; for this example use Node1. Enter yes to continue the update.
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Step 1
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After the confirmation screen from the last task displays, press Enter to continue. Enter yes when prompted to add network resources.
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Step 2
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From the Network Resources Menu, select Option 1: Add a Logical Hostname.
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If a failover resource group contains logical hostname resources, the most common configuration is to have one logical hostname resource for each subnet. Enter 1 to create a single resource.
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Step 3
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Step 4
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Press Enter to continue. The screen displays:
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clreslogicalhostname create -g ems-rg -p R_description="LogicalHostname resource for ems-service" ems-service
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Step 5
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Enter no when prompted to add any additional network resources.
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Step 1
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After the logical hostname confirmation screen, enter yes when prompted to begin adding data services.
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Step 2
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From the Data Services Menu select Option 1: EMSSCFO Server for Sun Cluster, and use the name ems-dsr for this example.
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Step 3
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Enter no when prompted to override the default.
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Step 4
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Step 1
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After the completion confirmation screen, press Enter to continue. Enter no when prompted to add any additional data service resources. Enter yes when prompted to manage and bring this resource group online.
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Step 2
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The process is now complete. At this point you can enter the scstat command to display the current online/offline status if required.
Important: Network administrators are advised that they should have any connected clients log out at this time. If clients cannot reconnect after the upgrade, please refer to the Troubleshooting appendix for information on any Java-related errors.This can be confirmed either by a software switchover, or by running the scstat command to confirm the current node status.
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Two Cluster Nodes: N-1 (initially this is the active node) and N-2 (initially this is the redundant node).
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A Resource Group managed by Web Element Manager exists. ems-rg is used for this example.
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A logical hostname and floating (shared) IP address has been configured on both servers. This example uses the default /etc/hosts folder. Use ems-service as the hostname for this example.
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Step 1
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Start with two server nodes: N-1 and N-2. They share both data files and database information. N-1 is currently active and N-2 is currently in standby mode, as shown below:
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Step 2
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With Web Element Manager running on N-1, put N-2 into maintenance mode (this is described in Removing an Inactive Node from the Resource Group below). Then upgrade WEM to version 12.0 or later.
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At this point, the database is not yet updated. In cluster mode, when WEM is upgraded on N-2 the postgres database is not started. so a new DB schema is not created. This is because the schema will be updated through the currently active server N-1 with SQL scripts that are provided as part of the installation package; this is explained in the section Updating the Databases. At this point N-2 is still in maintenance mode but now with updated WEM software, and the database schema has now been updated as shown below:
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Step 3
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To prepare for the switchover, take N-2 out of maintenance mode.
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Step 4
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To upgrade WEM on N-1, bring N-2 back into the cluster and do a switchover from N-1 to N-2 so now N-2 is the active host and WEM starts running processes.
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Step 5
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Now place the formerly active node N-1 into maintenance mode and upgrade WEM software while N-2 is the active node as shown below:
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Step 6
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Once the upgrade is complete, N-1 can be switched back to its role of active node if necessary by using the Cluster commands, or N-2 can continue as the active node.
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Important: Refer to the Installing the WEM Software chapter for more complete information about scripts and files. All configuration files placed in the <EMS_HOME>/server/etc folder and the script files in the <EMS_HOME>/server/scripts folder must be identical. This ensures that after the switch between servers, the behavior of EMS does not change in any way.Complete the following steps to remove N-2 from the Resource Group. Since the cluster resource group configuration will be same for both nodes, the cluster-related commands can be run on either node.
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Step 1
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Run the scstat command. scstat is used to verify the current status of the cluster resource group and ensures that on switchover/failover the servers will switch correctly. The following screen display reflects a properly configured cluster:
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Important: N-2 must not be allowed to run any WEM processes. This prevents the secondary node from taking ownership of resources. Removing it from the Resource Group prevents a failover from happening and N-1 continues to behave like a standalone WEM thus ensuring a successful upgrade. To do this:|
Step 2
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Step 3
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From the Resource Groups menu, select Option 8: Change the Properties of a Resource Group.
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Step 4
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Enter yes when prompted to continue.
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Step 5
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Step 6
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Select Option 1: Change the Nodelist Resource Group Properties
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Step 7
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Step 8
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The nodelist now contains only N-1. When prompted to update the nodelist property, enter yes. If your update was successful you will see the following screen confirmation:
Press Enter to continue. You will receive confirmation that only N-1 remains in the nodelist. Select Option q to Quit and exit back to the Resource Group Menu.
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Step 9
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From the Resource Group Menu select Option s: Show Current Status to confirm the current network resources if required.
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Step 1
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Copy the sqlfiles.tar file from the N-2 installation to a folder on N-1 and untar the file. This process is described fully in the Installing the WEM Software chapter.
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This will create a folder called sqlfiles.
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Step 2
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Step 3
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Step 5
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Step 6
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Press Enter.
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Step 7
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Important: Currently, this is port 5432, but this may change in a later release.Complete the following steps to return N-2 to the Resource Group and take over resource ownership in order to upgrade the software on N-1.
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Step 1
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Step 2
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From the Resource Groups Menu select Option 8: Change the Properties of a Resource Group.
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Step 3
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Enter yes when prompted to continue.
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Step 5
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Step 7
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Select Option 1: Add a Node/Zone to the Top of the Nodelist.
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Step 8
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Select Option 1: N-2.
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Step 9
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Enter yes when prompted to update the nodelist property.
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Step 10
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Step 1
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From the Resource Group Menu Select Option 5: Switch over a Resource.
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Step 2
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Scroll through the on-screen description and enter yes to continue.
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Step 4
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Select Option 1: Switch Group Ownership.
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Step 5
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Select the node to take ownership of ems-rg, which would be N-2. Enter yes to confirm. The screen will display the following message:
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Step 6
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Step 7
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From the Resource Group Menu select Option s Show Current Status. This shows that N-2 is now online and N-1 is offline.
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At this point return to Removing an Inactive Node from the Resource Group and begin the update process for N-1.
Important: Since the database schema were previously updated and both N-1 and N-2 share the same database, it is not necessary to run the SQL scripts again for N-1.This section provides instructions specific to a Symantec VCS installation to provide redundancy to multiple WEM servers. This software is documented by Symantec, and you will also need to refer to the Install, the Uninstall, and the Upgrade chapters in this guide. Server hardware requirements are in theWEM Port and Hardware Information chapter.
Important: Veritas Cluster is supported on both Sun servers using the Solaris Operating System and Cisco UCS servers using the RHEL OS. The VCS installation in this section is directed to installments on the RHEL platform. The VCS itself has a lot in common with the Solaris installation in the previous chapter; however, IPMP is proprietary software and supported only on the Solaris OS. A radio button on the installation screen allows the choice between a Solaris or a RHEL installation; for this reason, please use the GUI to perform the installation rather than the command line. 
Important: There are configuration changes required when installing WEM in Failover Mode rather than Standalone Mode. These re described in the Installing the WEM Software chapter. For this release, please use the GUI to perform the installation rather than the command line. |
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There is an example of a valid Main.cf configuration below
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Start installing the WEM application on the first cluster node using the instructions in the Installing the WEM Software section in this guide.
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Important: Make certain that the WEM application does not start after the installation is complete.|
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