Failover Support

jConnect supports the Adaptive Server failover.

Sybase Failover allows you to configure two Adaptive Servers as companions.

Note: Sybase Failover in a high availability system is a different feature than connection failover. Sybase strongly recommends that you read this section very carefully if you want to use both.

If the primary companion fails, the devices, databases, and connections for that server can be taken over by the secondary companion. You can configure a high availability system either asymmetrically or symmetrically.

An asymmetric configuration includes two Adaptive Servers that are physically located on different machines but are connected so that if one of the servers is brought down, the other assumes its workload. The secondary Adaptive Server acts as a “hot standby” and does not perform any work until failover occurs.
A symmetric configuration also includes two Adaptive Servers running on separate machines. However, if failover occurs, either Adaptive Server can act as a primary or secondary companion for the other Adaptive Server. In this configuration, each Adaptive Server is fully functional with its own system devices, system databases, user databases, and user logins.

In either setup, the two machines are configured for dual access, which makes the disks visible and accessible to both machines. You can enable failover in jConnect and connect a client application to an Adaptive Server configured for failover. If the primary server fails over to the secondary server, the client application also automatically switches to the second server and reestablishes network connections.

See Using Sybase Failover in High Availability Systems in the Adaptive Server Documentation for more detailed information.

When using jConnect as part of your failover strategy:

Have two Adaptive Servers configured for failover.
Only changes that were committed to the database before failover are retained when the client fails over.
Set the REQUEST_HA_SESSION jConnect connection property to true.
jConnect event notification does not work when failover occurs.
Close all statements when they are no longer used. jConnect stores information on statements to enable failover. Unclosed statements result in memory leaks.