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[SBR] How does the LDAP/SQL server target number determine when to activate the specified server?



Article ID: KB27024 KB Last Updated: 08 Mar 2017Version: 3.0
This article provides information on how the target number is determined, when multiple server instances are configured in the LDAP and SQL authentication files.

Note: This is only for the JDBC type of SQL connection, as the Oracle Client controls the number of connections and the activation of each connection.
The Target number that is associated with a server in the configuration file determines when it is activated; but certain servers are required to always be on and other servers have to activated, only when a failure occurs. How does this function and what is the proper configuration?
The Target number sets the activation priority of the server. SBR will read the [Server] section from the top down and activate each server with an activation number that is greater than the number of active server connections. In the following example, four servers have been configured:
When SBR is started and the .aut file is activated, SBR will read the [Server] section and see that s1=1. As no servers are connected and s1 has an target number of 1, then 1 is greater than 0; so SBR will connect to this server. Moving down the list, s2 is equal to 1 and SBR currently has 1 server connection; so, as 1=1, SBR will not activate this server.

Continuing down the list, server s3 is equal to 2 and SBR currently has 1 active connection to the s1 server. As 2 is greater than 1, SBR will connect to this server. Finally, s4=2 and 2=2; so this server connection will not be activated.

When SBR is started, the connections will look like this:
s1=1 ------> connected
s2=1 ------x not connected
s3=2 ------> connected
s4=2 ------x not connected
Now, if the s1 server fails, SBR will again use the activation number to determine which server has to be activated. The result will be as follows:
s1=1 ------x failed
s2=1 ------x not connected (Target number is not greater than the number of active connections)
s3=2 ------> Connected
s4=2 ------> Connected (Target number 2 is greater than the number of active connections after the failure)
At this point, the only time the s2 server will be connected is when the s1 server fails to load at startup or all of the other servers fail; making it a last resort server.
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