Where is the default location for the OC4J logs?

Question

Where is the default location for the OC4J logs?

Answer 1

Depends on what variant of the product you are using.
In an Oracle Applicaiton Server environment (ie the one you install versus unzip) the stdout/stderr streams from OC4J are captured in the $ORACLE_HOME/opmn/logs/<group-instance> directory.
If you are using standalone then stdout goes to the console where you started the process.
The logs for the OC4J instance itself are located in $ORACLE_HOME/j2ee/home/log/<instance_group> directory. In this directory you'll see different logs for differet areas of the server. Most of the logs however are captured in the oc4j sub-directory in the log.xml file. Whenever you enable an OC4J component logger in the j2ee-logging.xml file or via ASControl, this is where the logs will end up.
Take a look at the $ORACLE_HOME/j2ee/home/config/j2ee-logging.xml file -- the log handlers will give you some idea on the different log files that are in use.
You can configure your application loggers to also direct their log into this file if you wish. See http://buttso.blogspot.com/2007/09/directing-log-messages-into-oc4j.html for an example.