Managing Serviceguard Extension for SAP Version A.06.00 for Linux, December 2012

Resource) for each Replicated Enqueue. An EnqOR resource is refered to by the system as
sgesap.enqor_<SID>_ERS<INSTNR>.
Setting up the enqor MNP implements a protected follow-and-push behavior for the two packages
that include enqueue and its replication. As a result, an automatism will make sure that Enqueue
and its Enqueue Replication server are never started on the same node initially. Enqueue will not
invalidate the replication accidentally by starting on a non-replication node while replication is
active elsewhere. It is possible to move the package with the replication server to any free node
in a multi-node cluster without a requirement to reconfigure the enqueue package failover policy.
Figure 5 Visualization of a follow-and-push cluster in Serviceguard Manager
During failover of Enqueue, its replication is located dynamically and the Enqueue restarts on the
currently active replication node. Enqueue synchronizes with the local replication server. As a next
step, the package with the replication service shuts down automatically and restarts on a healthy
node, if available. In case of a failover in a multi-node environment, this implements a self-healing
capability for the replication function. Enqueue will failover to just any node from the list of statically
configured hosts if no replication package is running.
Two replication instances are required if Enqueue Replication Services are to be used for both the
JAVA stack and the ABAP stack. From this approach, several configuration options derive. In most
cases, it is the best practice to create separate packages for ASCS, SCS, and the two ERS instances.
It is also supported to combine the replication instances within one SGeSAP package. To combine
ASCS and SCS in one package, but only if the two ERS instances are combined in another package
is not supported. To combine ASCS and SCS in one package and keep the two ERS instances in
two separate packages is not supported. Otherwise, situations can arise in which a failover of the
combined ASCS/SCS package is not possible. Finally, ASCS cannot be combined with its ERS
instance (AREP) in the same package. For the same reason, SCS cannot be combined with its ERS
instance (REP).
SAP offers two possibilities to configure Enqueue Replication Servers:
14 SAP cluster concepts