Setting Up Database Server Groups for High-Availability Cluster Servers

When defining a high-availability cluster within Enterprise Replication, the cluster must appear to be a single logical entity within the replication domain. Define the servers within the same database server group in the sqlhosts file.

For example, Database Server Groups for Enterprise Replication with HDR illustrates two Enterprise Replication nodes, one of which is an HDR pair.
Figure 1: Database Server Groups for Enterprise Replication with HDR

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In this example, the HDR pair consists of the primary server, serv1, and the secondary server, serv1_sec. These two servers belong to the same database server group, g_serv1. The non-HDR server, serv2, belongs to the database server group g_serv2. The following example displays the sqlhosts file for this configuration: 

#dbservername    nettype    hostname     servicename  options
 g_serv1         group      -            -            i=1
 serv1           ontlitcp   machine1pri  port1        g=g_serv1
 serv1_sec       ontlitcp   machine1sec  port1        g=g_serv1
 g_serv2         group      -            -            i=2
 serv2           ontlitcp   machine2     port1        g=g_serv2
Important: If you use the g=server option in the group member definition, you can put the definition anywhere in the sqlhosts file.

Either HDR or Enterprise Replication can be set up first on the HDR pair serv1 and serv1_sec, but Enterprise Replication cdr commands must be run only on the primary server. If any cdr commands are attempted on the secondary server, a –117 error is returned: Attempting to process a cdr command on an HDR secondary server.