RMAN failed to connect target database with ORA-00020: maximum number of processes (150) exceeded

Today RMAN backup failed with following error, trailing error logs itself very self-explanatory.

Error logs:

RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of delete command at 11/14/2017 18:00:12
RMAN-12001: could not open channel ORA_DISK_1
RMAN-10008: could not create channel context
RMAN-10003: unable to connect to target database
ORA-00020: maximum number of processes (150) exceeded

Solution:

Increase number of processes from sys user with sysdba privilege.

SQL> show parameter processes;
NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
....
processes                            integer     150

SQL> alter system set processes=300 scope=spfile;
System altered.

Bounce the database so changes will be reflected in database instance and then you can initiate RMAN backup.