Creating an SAP Resource Hierarchy

*IMPORTANT: In keeping with industry best practices and announced with the release of v9.6.2, beginning with v9.7.0 SIOS will no longer support new or existing configurations with NFS servers/clients on the same nodes as the SAP services when setting up an SAP system (also known as “loopback configuration”). Instead, we require using alternate configurations such as:
• EFS in AWS
• Azure Premium File Shares with NFS

• Google NFS Share
• NFS as a separate cluster

To protect the SAP System, an SAP Hierarchy will be needed. This SAP Hierarchy consists of the Core (Central Services) Resource, the ERS Resource, the Primary Resource and Secondary Resources. To create this hierarchy, perform the following tasks from the Primary Server.
Note: The below example is meant to be a guideline for creating your hierarchy. Tasks will vary somewhat depending upon your configuration.

Create the Core Resource

1. From the LifeKeeper GUI menu, select Edit, then Server. From the drop-down menu, select Create Resource Hierarchy.

A dialog box will appear with a drop-down list box with all recognized recovery kits installed within the cluster. Select SAP from the drop-down listing.

Click Next.

When the Back button is active in any of the dialog boxes, you can go back to the previous dialog box. This is especially helpful should you encounter an error that might require you to correct previously entered information.

If you click Cancel at any time during the sequence of creating your hierarchy, LifeKeeper will cancel the entire creation process.

2. Select the Switchback Type. This dictates how the SAP instance will be switched back to this server when it comes back into service after a failover to the backup server. You can choose either intelligent or automatic. Intelligent switchback requires administrative intervention to switch the instance back to the primary/original server. Automatic switchback means the switchback will occur as soon as the primary server comes back on line and re-establishes LifeKeeper communication paths.

The switchback type can be changed later, if desired, from the General tab of the Resource Properties dialog box.

Click Next.

3. Select the Server where you want to place the SAP PAS, ASCS or SCS (typically this is referred to as the primary or template server). All the servers in your cluster are included in the drop-down list box.

Click Next

4. Select the SAP SID. This is the system identifier of the SAP PAS, ASCS or SCS system being protected.

Click Next.

5. Select the SAP Instance Name (ex. ASCS<No.>) (Core Instance first) for the SID being protected.

Note: Additional screens may appear related to customization of Protection and Recovery Levels.

6. Select the IP Child Resource. This is typically either the Virtual Host IP address noted during SAP installation (SAPINST_USE_HOSTNAME) or the IP address needed for failover.

a. Select whether LifeKeeper should attempt to automate creation of dependent filesystems for the instance. If yes is selected, LifeKeeper will attempt to create the necessary filesystem resources and add them as dependencies under the SAP resource. (Note that replicated filesystems cannot be created automatically.) Normally yes is selected only when using shared storage such as FibreChannel or iSCSI. If no is selected, the following dialog box will prompt the user to select existing LifeKeeper filesystem resources to be added as dependencies.

b. If no was chosen in the previous dialog, the option will be provided to select the filesystem resource(s) which should be added as a dependency under the SAP resource. Multiple resources can be selected by holding CTRL and clicking each resource separately. Note: Filesystem resources must be in-service (ISP) on this server in LifeKeeper in order to appear as choices in this dialog.

The network shared device is automatically mounted by the systems so does not require a LifeKeeper dependency.

7. Select or enter the SAP Tag. This is a tag name that LifeKeeper gives to the SAP resource. You can select the default or enter your own tag name. The default tag is SAP-<SID>_<INST>.

When you click Create, the Create SAP Resource Wizard will create your SAP resource.

8. Another information box will appear explaining that you have successfully created an SAP resource hierarchy, and you must Extend that hierarchy to another server in your cluster in order to place it under LifeKeeper protection.

When you click Next, LifeKeeper will launch the Pre-Extend Wizard that is explained later in this section.

If you click Cancel now, a dialog box will appear warning you that you will need to come back and extend your SAP resource hierarchy to another server at some other time to put it under LifeKeeper protection.

9. The Extend Wizard dialog will prompt for each resource in the hierarchy. First it will ask for the switchback type for the target system similar to the prompt when creating on the template server (node-b in this example).

The Template Priority of 1 shows that node-b is the highest priority server for this hierarchy.

The Target Priority of 10 shows that node-a has a lower priority for this hierarchy.

The extend wizard will check that all resources in the hierarchy can be extended to the selected target. In this example the IP resource was already extended to node-a as the pre-extend script identifies below:

The wizard will then run the extend for each resource in the hierarchy. Since the IP resource was already extended to node-a there are no prompts for the IP resource. Click next to proceed through each resource wizard.

Select Extend to add the resources to the target system. The final Extend Wizard will appear stating Hierarchy successfully extended. Click Finish.

10. The Hierarchy Integrity Verification dialog appears.

Once Hierarchy Verification finishes, click Done to exit the Create Resource Hierarchy menu selection.

Hierarchy with the Core as the Top Level

Create the ERS Resource

The ERS resource provides additional protection against a single point of failure of a Core Instance (Central Services Instance) or enqueue server process. When a Core Instance (Central Services Instance) fails and is restarted, it will retrieve a backup copy of the enqueue lock table (i.e., the replication table) from the enqueue replication server. The result is that, in the event of the enqueue server failure, no transactions or updates are lost and the service for the SAP system continues.

For a discussion of the differences in the implementation of ERS resources in LifeKeeper for Linux in versions 9.4.0 and later versus the implementation prior to version 9.4.0, see ERS Resource Types in LifeKeeper.

!Important Note: The creation and extension of the ERS hierarchy must occur on a server where the corresponding ASCS/SCS instance is not in-service (ISP) in LifeKeeper. In the case of ERSv2, the underlying ERS filesystem resources must first be brought in-service on the backup server where the resource will be created.

Perform the following steps to create the ERS Resource.

1. From the LifeKeeper GUI menu, select Edit, then Server. From the drop-down menu, select Create Resource Hierarchy. A dialog box will appear with a drop-down list box with all recognized recovery kits installed within the cluster. Select SAP from the drop-down listing. Click Next.

2. Select the Switchback Type. Click Next.

3. Important: Select a Server in the cluster where the corresponding ASCS/SCS instance is not ISP. Click Next.

4. Select the SAP SID for the ERS instance. Click Next.

5. Select the SAP Instance Name (ex. ERS<No.>). Click Next.

6. If creating a resource to represent an ERSv2 instance, select the IP Child Resource. This choice will not appear when creating a resource to represent an ERSv1 instance.

7. If creating a resource to represent an ERSv2 instance, select the Dependent Filesystem Resource to be added as a dependency under the ERS resource. Note that filesystem resources must be in-service (ISP) on this server in LifeKeeper in order to appear on this list. This choice will not appear when creating a resource to represent an ERSv1 instance.

The EFS file system is automatically mounted by the systems so does not require a LifeKeeper dependency.

8. Select or enter the SAP Tag.

9. Select Create.

10. Follow prompts to extend resource hierarchy. Note: A resource representing an ERSv1 instance may only be extended to one backup server. The hierarchy extension will fail if attempting to extend an ERSv1 hierarchy to a third cluster node.

11. Once Hierarchy Successfully Extended displays, select Next Server if extending to a third node or Finish.

12. Select Done.

Separate ASCS and ERSv1 Hierarchies

Separate ASCS and ERSv2 Hierarchies

In the case where the ASCS instance is running ENSAv2, the ERS instance is running ERSv2, and the hierarchies have been extended to the same systems in a cluster with three or more nodes, the ASCS and ERS resource hierarchies can be forced to attempt to avoid each other on switchover and failover by using special “hierarchy avoidance” generic application resources. Note: These hierarchy avoidance resources should not be used in an ENSAv1/ERSv1 configuration or in a 2 node cluster. The following is a 3 node cluster with the “hierarchy avoidance” resources configured:

Create the Primary Application Server Resource

1. Again, for this same SAP SID, repeat the above steps to create the Primary Application Server Resource selecting DVEBMGS{XX} (where {XX} is the instance number) when prompted.

2. Select the Level of Protection when prompted (default is FULL). Click Next.

3. Select the Level of Recovery when prompted (default is FULL). Click Next.

4. When prompted for Dependent Instances, select the “parent” instance, which would be the ERS instance created above.

5. Select the IP Child Resource.

6. Follow prompts to extend resource hierarchy.

7. Once Hierarchy Successfully Extended displays, select Finish.

8. Select Done.

Hierarchy with Primary Application Server as Top Level

Create the Secondary Application Server Resources

If necessary, create the Secondary Application Server Resources in the same manner as above.

Note: For command line instructions, see Setting Up SAP from the Command Line.

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