Got this error.
Try to connect your database server directly.Definitely you will get this error.
Enter user-name: sys as sysdba
ORA-00020: maximum number of processes (250) exceeded
you need to down your listener
Try to login directly using sqlplus
If that not possible
Then ... shutdown your db service
After that increase your number of processes
SQL>ALTER SYSTEM SET PROCESSES=350 SCOPE=SPFILE;
you must shutdown after this commands for changing this parameter.