Oracle error
ORA-12537
ORA-12537: TNS:connection closed
What usually causes it
The connection dropped during the handshake: valid node checking, the PROCESSES limit, a firewall, or permissions on the oracle binary.
What to check first
Check the listener log and TCP.VALIDNODE_CHECKING in sqlnet.ora.
Scripts that help
- Processes and sessions against their limitsCurrent and peak usage of processes, sessions and transactions since startup. A PEAK % near 100 means the next connection storm will hit ORA-00020.
- Rotate the listener logTurns listener logging off, lets you rename the current listener.log, then turns logging back on so a fresh file starts. Run it from the OS prompt as…