This chapter describes client/server interaction and how to modify applications that make Open Client/Client-Library calls to support clusters. It describes using isql in a shared-disk cluster environment.
DB-Library can connect to an instance in a shared-disk
cluster, but does not support the Sybase shared-disk or high-availability
functionality.
The version of Open Client™, jConnect™ for JDBC™, ODBC, OLE DB, and ADO.NET that ships with the Cluster Edition supports:
Login redirection – the ability of an instance to redirect an incoming client connection to another instance prior to acknowledging the login. Login redirection occurs during the login sequence. The client application does not receive notification that it was redirected.
Connection migration – occurs when an existing client is transferred from one instance of a cluster to another. See “Connection migration” for information about when migration can occur, and connection criteria.
Extended high-availability failover – in an extended failover configuration, Adaptive Server provides a list of failover addresses to “high-availability-aware” clients when they connect. This allows high-availability-aware clients or applications to failover multiple times if the instance to which they are connected fails.
These clients are not required to have a HAFAILOVER entry in their interfaces file or directory services. However, if they do have an HAFAILOVER entry in their interfaces file or directory services, the clients continue to use this entry until Adaptive Server sends them a list of failover addresses or servers to connect to. The clients always use the latest list Adaptive Server provides.
To implement login redirection and connection migration, make sure the application uses a current copy of the client libraries:
If the application is linked to shared libraries – include the new client libraries in the library search path before the old libraries.
If the application is statically linked – relink the application.
Use the CS_PROP_MIGRATABLE connection property to enable or disable connection migration. CS_PROP_MIGRATABLE is on by default. See the Client Library Reference Manual.
To implement extended failover, make sure the application uses a current copy of the client libraries and that you have enabled high availability. See Using Sybase Failover in a High Availability System for information about enabling high availability.
For information about using the failover features with jConnect, ODBC, OLE DB, and ADO.NET Driver, see “New Features Open Server 15.0 and SDK 15.0 for Microsoft Windows, Linux, and UNIX”
