TNS-12520: TNS:listener could not find available handler for requested type of server

Hi,

Sometimes You can get “TNS-12520: TNS:listener could not find available handler for requested type of server  ” error.

Details of error are as follows.

TNS-12520: TNS:listener could not find available handler for requested type of server

This error is related with out of available Oracle processes.

If processes parameters are insufficient, then you should increase the PROCESSES parameter as follows.

SQL> show parameter processes

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
aq_tm_processes integer 1
db_writer_processes integer 1
gcs_server_processes integer 0
global_txn_processes integer 1
job_queue_processes integer 1000
log_archive_max_processes integer 4
processes integer 1500
SQL>
SQL>
SQL> alter system set processes=2000 scope=spfile;

System altered.

SQL>

Restart database after this operation.

Sometimes the reason of this error is due to a network hardware error, so check your network.

Do you want to learn more details about RMAN, then read the following articles.

https://ittutorial.org/rman-backup-restore-and-recovery-tutorials-for-beginners-in-the-oracle-database/