Managing HP Serviceguard Extension for SAP for Linux, December 2013

• Start and stop packages on each configured node. When testing SGeSAP follow-and-push
mechanism the enqor MNP package must be up. This will restrict the possible nodes for SCS
and ERS package startup.
• Make sure client applications (dialog instances) can connect
5.5.11 Configuring sgesap/sapextinstance, sgesap/sapinfra and sgesap/livecache
This section describes configuring SGeSAP toolkit with sgesap/sapextinstance, sgesap/sapinfra
and sgesap/livecache parameters.
5.5.11.1 Remote access between cluster nodes and to external application servers
For external applications servers configured in a package, remote access between the cluster nodes
and between external hosts needs to be enabled. Root access between cluster hosts must be enabled
and the users <sid>adm and root from the cluster (in this case also a cluster host can assume the
role of an external appserver) must be allowed to run as <sid>adm on the from external
application servers. It is recommended to use ssh(1). Usage of rsh is discouraged.
To accomplish this, the following steps are necessary:
• Create ssh keys for root and <sid>adm
• Distribute those keys to allow access
To generate the keys as root user and as <sid>adm user run the ssh-keygen –t rsa command
on each host.
This will create files for the private (id.rsa) and public key (id_rsa.pub) in the user’s .ssh directory.
The public key then needs to be distributed to the other hosts. This can be accomplished by running
the command ssh-copy-id –i id_rsa.pub user@host. This will add the user’s public key
to the authorized_keys (not authorized_keys2) on the target host.
On each cluster node this has to be executed as the root user and host being one of the other
cluster nodes in turn. On each clusternode and for each external application server invoke the
ssh-copy-id … user@host command twice, replacing the user@host string with
<sid>adm@appserver and root@appserver.
It is also recommended to pre-populate the known hosts file (/etc/ssh/ssh_known_hosts) on each
cluster node by executing
ssh-keyscan list-of-remote-hosts >> /etc/ssh/ssh_known_hosts
This avoids the first login from the remote host hanging in fingerprint confirmation.
After you complete this section, you can login without using the password for:
• root user on all cluster nodes
• root and sidadm on external application servers.
5.5.11.2 Configuring external instances (sgesap/sapextinstance)
External dialog instances ("D" and "J" type) can be configured into an SGeSAP package using
the sgesap/sapextinstance module. These instances might have the same SID as used for
the package (values for thesap_ext_system and sap_system parameters are identical), or
the SID can be from a different instance (the values for sap_ext_system and sap_system
parameters are different). The external dialog instances can be started, stopped, and restarted
using the package, and also stopped when the package fails over to the node where the instance
is running. A restriction that applies to instances with a foreign SID is that these can only be stopped
if the package fails on the local node.
Any instances configured with the sapextinstance module are handled on a best effort basis.
Failing to start or stop an external instance will not cause the whole package to fail. Such instances
are also not monitored by a SGeSAP service monitor. If the sapcontrol usage attribute is enabled
80 Clustering SAP Netweaver using SGeSAP packages