IBM DB2 Manual page 107

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v For the first connection to IBM Informix Dynamic Server:
a. The application specifies a server and port for the initial connection.
Those values identify a Connection Manager.
b. The IBM Data Server Driver for JDBC and SQLJ uses the information
from the Connection Manager to obtain information about the primary
and alternate servers. IBM Data Server Driver for JDBC and SQLJ loads
those values into memory.
c. If the initial connection to the Connection Manager fails:
– If the clientRerouteAlternateServerName and
clientRerouteAlternatePortNumber properties are set, the IBM Data
Server Driver for JDBC and SQLJ connects to the Connection Manager
that is identified by clientRerouteAlternateServerName and
clientRerouteAlternatePortNumber, and obtains information about
primary and alternate servers from that Connection Manager. The IBM
Data Server Driver for JDBC and SQLJ loads those values into memory
as the primary and alternate server values.
– If the clientRerouteAlternateServerName and
clientRerouteAlternatePortNumber properties are not set, and a JNDI
store is configured by setting the property
clientRerouteServerListJNDIName on the DB2BaseDataSource, the IBM
Data Server Driver for JDBC and SQLJ connects to the Connection
Manager that is identified by
DB2ClientRerouteServerList.alternateServerName and
DB2ClientRerouteServerList.alternatePortNumber, and obtains
information about primary and alternate servers from that Connection
Manager. IBM Data Server Driver for JDBC and SQLJ loads the
primary and alternate server information from the Connection
Manager into memory.
d. If clientRerouteAlternateServerName and
clientRerouteAlternatePortNumber are not set, and JNDI is not
configured, the IBM Data Server Driver for JDBC and SQLJ checks DNS
tables for Connection Manager server and port information. If DNS
information exists, the IBM Data Server Driver for JDBC and SQLJ
connects to the Connection Manager, obtains information about primary
and alternate servers, and loads those values into memory.
e. If no primary or alternate server information is available, a connection
cannot be established, and the IBM Data Server Driver for JDBC and
SQLJ throws an exception.
v For subsequent connections, the IBM Data Server Driver for JDBC and SQLJ
obtains primary and alternate server values from driver memory.
2. The IBM Data Server Driver for JDBC and SQLJ attempts to connect to the data
source using the primary server name and port number.
If the connection is through the DriverManager interface, the IBM Data Server
Driver for JDBC and SQLJ creates a DataSource object for client reroute
processing.
3. If the connection to the primary server fails:
a. If this is the first connection, the IBM Data Server Driver for JDBC and
SQLJ attempts to reconnect to the original primary server.
b. If this is not the first connection, the IBM Data Server Driver for JDBC and
SQLJ attempts to reconnect to the new primary server, whose server name
and port number were provided by the server.
Chapter 3. JDBC application programming
91