Managing HP Serviceguard Extension for SAP for Linux, December 2013

The secondary package startup operation will fail if it cannot establish an initial connection with
the primary system to resynchronize the local data. A secondary package will not fail if there is
no primary instance available, but it will attempt to start the secondary instance once the primary
system is available.
If you manually halt the secondary package on the node configured as the secondary system, this
will not stop the instance of the secondary system. However, the secondary instance will no longer
be monitored.
Command to halt secondary package on the node:
# cmhaltpkg hdbs<SID>
Stop and restart the local HANA instances manually with standard SAP tools, the same way as
the primary systems.
If you attempt to restart during secondary package uptime and primary system downtime, the
restart will not be successful; this is because a secondary instance will refuse to start if its primary
instance is not reachable. In this situation, the secondary package will create an alert that the
secondary instance is down. The secondary package will not fail, but it will attempt to finalize the
start of the secondary instance once the primary system is available.
3.7.3 Manual operations on the production system
1. To move the production environment to the second node (takeover):
# cmhaltpkg hdbs<SID>
# cmhaltpkg hdbp<SID>
# cmrunpkg –n <node_2> hdbp<SID>
# cmmodpkg –e hdbp<SID>
As part of this operation sequence, the original primary system is stopped; the active secondary
system will take over and become a primary system. The cluster services for the production
system are activated including network accessibility for production clients. Enabling cluster
run commands (cmruncl), node run commands (cmrunnode), and primary package autorun
(cmmodpkg –e hdbp<SID>) will not result in an automatic takeover if an active primary
system is available on one of the two nodes. This behavior is implemented to ensure that
takeovers are not accidentally triggered.
2. To move the secondary system (demotion):
# cmrunpkg –n <node_1> hdbs<SID>
# cmmodpkg –e hdbs<SID>
The previous primary system will subsequently become the new secondary system by starting
the secondary package on its node. As part of this operation sequence, the original primary
instance is on halt, demoted, and registered as secondary instance, and then restarted.
Depending on the availability and accuracy of local data, this operation causes significant
workload on the replication network and the disk sub-systems of both the appliances.
In this scenario, it is possible that the system is updated with delta data shipments from the
new primary node, which restricts the exchange of the altered data during takeover and
demotion. If the local data set is corrupt or if it was altered after the takeover operation, a full
re-initialization is triggered. This will take some time, similar to the initialization time of a new
replication, because the complete data files of the primary database are transferred through
the replication network.
34 SAP cluster administration