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Hostname/IP address issues with Disaster Recovery

In our disaster recovery procedure, we will activate a stand-by database located to another host than the production servers. In order not to change the hostname/IP address, we are thinking on the following processes:
DNS

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alias will be created for the Prod instance, with an IP address associated to this instance. In case of activation of the stand-by database, the IP address will be transferred to the server that hosts the stand-by database. This will allow transparent reconnection for our users. We are running tests, but we would like to have your input/recommendations on that. The idea is to have one alias/IP address dedicated to a SAP instance. Hostname will be different with another IP address. Thanks for any advice you may have.


What I usually do it set up the hostname different from the hostname as known by SAP.

Physical Hostname
a) primary = unix01
b) failover = unix02 Hostname as known to SAP = unix03 (in all profiles, etc.)

That way, nothing within SAP has to be reconfigured once you failover.

Users will be told to contact unix03 which will be associated with either the primary or failover depending on the situation.

Be sure to check out the SAP parameters (for the main profile):
gw/alternative_hostnames = unix01,unix02,unix03
SAPLOCALHOST = unix03
SAPLOCALHOSTFULL = unix03

In the sidadm home directory you will need
startsap_unix01_01, stopsap_unix01_01
startsap_unix02_01, stopsap_unix02_01
since the alias is configured to look for the physical hostname.

Keep in mind that if you ever do an upgrade, you will also need startsap_unix03_01, and stopsap_unix03_01 since the upgrade program is configured to start and stop the system in this way. Hope this helps!


This was first published in May 2002

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