Strategies for increasing availability with Connection Managers

You can increase the resiliency of your client/server communication environment.

Install multiple network-interface cards (NICs) on client, Connection Manager, and database-server hosts

You can prevent a network-connectivity failure by installing multiple NICs on each host in a connection-management domain. If a NIC fails, the host can use other available NICs.

Install multiple Connection Managers

You can prevent a Connection Manager from becoming a single point of failure in your system by installing multiple Connection Managers to manage a domain.

Install Connection Managers separate from database servers

To prevent simultaneous Connection Manager and database server failure if a host fails, install Connection Managers on hosts that are not running database servers.

Use keywords in Connection Manager service-level-agreements

If a Connection Manager manages a high-availability cluster, you can use the cluster keywords to maintain connection consistency after failover. If database servers in a cluster switch roles after failover, the Connection Manager can use cluster keywords to continue directing client connection requests to the appropriate cluster-server type.

The cluster keywords are:
  • HDR - High-availability data replication server
  • RSS - Remote standalone secondary server
  • SDS - Shared-disk secondary server
  • PRI - Primary server
  • PRIMARY - Primary server

Use group entries in sqlhosts files and Connection Manager configuration files

Create database-server groups in the host sqlhosts file of each Connection Manager that manages a high-availability cluster. Then, specify sqlhosts groups, rather than individual server names, in Connection Manager configuration files. If you specify database server names for a connection unit's ONEDB_SERVER parameter, and those specified servers are offline when a Connection Manager restarts, the Connection Manager is unable to reconnect to the cluster. If you specify a sqlhosts group for a connection unit's ONEDB_SERVER parameter, and at least one of the group's database servers is online when a Connection Manager restarts, the Connection Manager can reconnect to the cluster.

Specify the c=1 option for sqlhosts group entries so that the connection-attempt starting point for a list of group members is random. For example:
#dbservername   nettype    hostname   servicename   options
 my_servers     -          -                        c=1
 server_1       onsoctcp   host_1     port_1        g=my_servers
 server_2       onsoctcp   host_2     port_2        g=my_servers
 server_3       onsoctcp   host_3     port_3        g=my_servers