Connections between the client and the database may hang unexpectedly due to firewall or application problems between the Oracle database and the client. In this case, the database will write too many “TNS-00505: Operation timed out” errors in the alert.log file.
To solve the problem, the following line should be added to the sqlnet.ora file under the TNS_ADMIN (ORACLE_HOME / network / admin) directory where the database is running (not the grid), and the listeners and the database on the servers running the database should be restarted.
The content of a sample sqlnet.ora file should be as follows.
NAMES.DIRECTORY_PATH= (TNSNAMES, EZCONNECT) ADR_BASE = /u01/app/oracle SQLNET.EXPIRE_TIME=10 SQLNET.ALLOWED_LOGON_VERSION_SERVER=8 SQLNET.ALLOWED_LOGON_VERSION_CLIENT=8
After modifying or creating the sqlnet.ora file, restart the database first and then the listener services on all nodes.