Connection failover

Connection failover allows a client application to switch to an alternate Adaptive Server if the primary server becomes unavailable due to an unplanned event, like power outage or a socket failure. In a cluster environment, client applications can fail over numerous times to multiple servers using dynamic failover addresses.

With high availability option enabled, the client application does not need to be configured to know the possible failover targets. Adaptive Server keeps the client updated with the best failover list based on cluster membership, logical cluster usage, and load distribution. During failover, the client refers to the ordered failover list while attempting to reconnect. If the driver successfully connects to a server, the driver internally updates the list of host values based on the list returned. Otherwise, the driver throws a connection failure exception.

You can use the connection string to enable connection failover by setting REQUEST_HA_SESSION to true. For example:

URL="jdbc:sybase:Tds:server1:port1,server2:port2,...,
serverN:portN/mydb?REQUEST_HA_SESSION=true"

where server1:port1, server2:port2, ... , serverN:portN is the ordered failover list.

In establishing a connection, jConnect attempts to connect to the first host and port specified in the failover list. If unsuccessful, goes through the list until a connection is established or until the end of the list is reached.