$ oerr ora 00020
00020, 00000, "maximum number of processes (%s) exceeded"
// *Cause:  All process state objects are in use.
// *Action: Increase the value of the PROCESSES initialization parameter.

SQL> SELECT *
  2    FROM v$resource_limit
  3   WHERE resource_name = 'processes'
  4  /

RESOURCE_NAME   CURRENT_UTILIZATION MAX_UTILIZATION INITIAL_AL LIMIT_VALU
--------------- ------------------- --------------- ---------- ----------
processes                        19              25        150        150