Purposeof sqlnet.expire_time parameter is to "Determines time interval to send a probe to verify the session is alive".
Default: None
Minimum Value: 0 minutes
Recommended Value: 10 minutes
Example: sqlnet.expire_time=10
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You are not going to get information from using this parameter in sqlnet.ora file. Best is to turn the tracing on at support level and start database. Please check Oracle alert log and listener.log file before you proceed with more investigation.
I hope this helps.
Cheers!!!
Mohammad Zahid
Software Developer
Database Management Applications.
Vancouver, Canada
E-mail: mzahid@shaw.ca