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AdministeringIn addition to administering the database server, you can tune performance, replicate data, and archive data.
System administrationThese topics contain concepts, procedures, and reference information for database and database server administrators to use for managing and tuning HCL Informix® database servers.
Administrator's GuideThe Informix® Administrator's Guide provides the information required to administer HCL Informix®.
High availability and scalabilityA successful production environment requires database systems that are always available, with minimal if any planned outages, and that can be scaled quickly and easily as business requirements change.
Cluster failover, redirection, and restorationTo maintain availability, you must plan for the failover of primary servers, redirecting client connections from unavailable servers, and restoring the cluster to its original configuration after a failure.
Redirection and connectivity for data-replication clientsWhen any server in a high-availability cluster becomes unavailable, any client connections to it should be redirected to an available server. The best way to handle connection redirection is to use Connection Manager to automatically reconnect client connections to the servers that you specify in service level agreements. Alternatively, you can control connection redirection with environment variables or connection information.
Redirecting clients with the INFORMIXSERVER environment variableThe INFORMIXSERVER environment variable redirection method can be used when an application does not explicitly specify a database server in the CONNECT statement, so that the client connects to the database server that the INFORMIXSERVER environment variable specifies.

Redirecting clients with the INFORMIXSERVER environment variable

The INFORMIXSERVER environment variable redirection method can be used when an application does not explicitly specify a database server in the CONNECT statement, so that the client connects to the database server that the INFORMIXSERVER environment variable specifies.

If one of the database servers in a cluster is unusable, applications that use that database server can reset their INFORMIXSERVER environment variable to the another database server in the cluster to access the same data.

Applications read the value of the INFORMIXSERVER environment variable only when they start. Therefore, applications must be restarted to recognize a change in the environment variable.

To support this method of redirection, you can use the following connectivity statements:

CONNECT TO DEFAULT
CONNECT TO database

You cannot use the CONNECT TO database@dbserver or CONNECT TO @dbserver statements for this method. When a database server is explicitly named, the CONNECT statement does not use the INFORMIXSERVER environment variable to find a database server.

Administrators take no action to redirect the clients, but they might be required to change the type of the database server.

Users who are running client applications must perform the following three steps when they decide to redirect clients with the INFORMIXSERVER environment variable.

To redirect clients with the INFORMIXSERVER environment variable:

Quit their applications.
Change their INFORMIXSERVER environment variable to hold the name of the other database server in the replication pair.
Restart their applications.

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