Managing HP Serviceguard Extension for SAP for Linux, December 2013

content got lost. As a reaction they cancel ongoing transactions that still hold granted locks. These
transactions need to be restarted.
Enqueue Replication provides a concept that prevents the impact of a failure of the Enqueue Service
on the Dialog Instances. Thus transactions no longer need to be restarted. The Enqueue Server has
the ability to create a copy of its memory content to a Replicated Enqueue Service that needs to
be running as part of a Enqueue Replication Service Instance (ERS) on a remote host. This is a
realtime copy mechanism and ensures that the replicated memory accurately reflects the status of
the Enqueue Server at all times.
There might be two ERS instances for a single SAP system, replicating SCS, and ASCS locks
separately.
Figure 4 Follow-and-push failover concept for ABAP and JAVA instances
Node 1 Node 2 Node 3
follow
follow
push
push
SGeSAP Cluster
Automated Replicated Enqueue
Application Servers
ascsC11
scsC11
dbC11
ers00C11
d04C11
ers01C11
d03C11
SAP enqor multi-node package
Shared Disks
LAN
JD04
NOTE: If Enqueue Services are configured as an integral part of an ABAP DVEBMGS Central
Instance will not be able to utilize replication features. The DVEBMGS Instance needs to be split
up in a standard Dialog Instance and a ABAP System Central Service Instance (ASCS).
The SGeSAP packaging of the ERS Instance provides startup and shutdown routines, failure
detection, split-brain prevention and quorum services to the mechanism. SGeSAP also delivers a
service monitor sapenqor.mon that is meant to be configured as the sole part of a enqor multi-node
package. This MNP maintains a generic resource of type EnqOR (Enqueue Operation
Resource) for each Replicated Enqueue. An EnqOR resource is referred to by the system as
sgesap.enqor_<SID>_ERS<INSTNR>.
2.5 Example 3: Follow-and-push with automated enqueue replication 15