[Informix] How do I always connect to primary server in MACH11/HDR cluster environment -- Posted by inturi on Friday, July 11 2008
You can do this two ways.

1> Configure Connection manager, and SLA rule to always connect to primary server.
Please see connection manager details here.

2> Configure group for HDR/MACH11 cluster,add all MACH11/HDR server entries under the group in INFORMIXSQLHOSTS file, and always connect to the group name instead of individual server names under MACH11/HDR cluster.

Clients always connect to the primary server if you use group name in connect statement.

Here is an example INFORMIXSQLHOSTS file with group configuaration:

g_mach11 group - - i=10
myprim ontlitcp primhost prim_port g=g_mach11
hdr ontlitcp hdrhost hdr_port g=g_mach11
sds1 ontlitcp sds1host sds1_port g=g_mach11