I faced with that issue on 12c database. Error message detail is:
TNS-00505: Operation timed out

Here is the solution:


To solve this error, follow below steps

  1. Set the following parameters in the sqlnet.ora which is under $ORACLE_HOME/network/admin path. If file is not exist then you can create it by your oracle software owner

SQLNET.INBOUND_CONNECT_TIMEOUT=600

SQLNET.EXPIRE_TIME= 25

  1. You may also add below line into your listener.ora file under $ORACLE_HOME/network/admin.

INBOUND_CONNECT_TIMEOUT_=600

Reference:
Alert Log Errors: 12170 TNS-12535/TNS-00505: Operation Timed Out (Doc ID 1628949.1)