The log configuration file name is:
portal_server_data_directory/config/portal_ID/config/PSLogConfig.properties
Example: /var/opt/SUNWportal/portals/myPortal/config/PSLogConfig.properties
The log file location is:
portal_server_data_directory/portals/portal_ID/logs/instance_ID
Example: /var/opt/SUNWportal/portals/myPortal/logs/myInstance/
By default, one file is created. The file name is portal.0.0.log. The content is logged through PortletContext.log().