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Lesson 8 The sqlnet.ora file, part 2
Objective Describe the characteristics of the sqlnet.ora file for an Oracle server.

sqlnet.ora File Parameters

TRACE_LEVEL_client = 16
TRACE_LEVEL_server = 16
TRACE_DIRECTORY_CLIENT = /ora8/dba/oracle/
LOG_DIRECTORY_CLIENT = /ora8/dba/oracle/
names.default_domain = world

The code listed above examines the parameters that describe a typical sqlnet.ora file for an Oracle server.
While all of the SQL*Net parameters are self-explanatory, there are some that are more important than others:
  1. Trace levels (client and server) specify the amount of detail SQL*Net will provide in the trace files. The larger the number, the greater the detail. We will cover this in depth later in the course.
  2. Directory locations tell SQL*Net where to place the log and trace files. If you do not specify a default directory for trace files, they will be placed in your current directory on the UNIX server. For example, a UNIX user called FRED would find his trace file in the home directory for the FRED user unless he specified another directory. Hence, it is a good idea always to specify the trace and log directory locations. If the locations are not specified (or if you do not have a sqlnet.ora file), the logs are directed to $ORACLE_HOME/rdbms/log.
  3. Expire time is an optional parameter that determines how often SQL*Net sends a probe to verify that a client/server connection is still active. If a client is abnormally terminated, a connection may be left open indefinitely unless identified and closed by the system. If this parameter is specified, SQL*Net sends a probe periodically to determine whether there is an invalid connection that should be terminated.

Note: The expire_time parameter only polls from the server to the client. Hence, when a connection goes down, the server process will terminate, but the client screen may terminate with any number of strange messages.

Dead connection detection
Dead connection detection

In the illustration above, we see the expire_time=10, meaning that Net will send a "ping" to the client once every 10 minutes. If there is no response, the Oracle process is terminated and the session to Oracle is closed. There are at least two circumstances under which this may occur:
  1. The network connection to the server is lost.
  2. The UNIX connection to Oracle is lost. (This is called a "zombie" process.)
Now that we haved covered the basics of the parameter files, let us look at how processes are established between Oracle clients and servers.

Master Tnsnames.ora File - Exercise

Before moving on to the next lesson, click the Exercise link below to practice working with sqlnet.ora and tnsnames.ora files.
Master Tnsnames.ora File - Exercise