BPEL / Oracle XE: ORA-12516, TNS:listener could not find available handler with matching protocol stack(Metalink ID 431422.1)

Symptoms
You are using Oracle XE database for the orabpel schema, but BPEL fails frequently with the following error:
java.sql.SQLException: Listener refused the connection with the following error:
ORA-12516, TNS:listener could not find available handler with matching proto stack

Cause
The Oracle XE Database is configured by default to run only 20 or 40 PROCESSES; the maximum load for dedicated connections is determined by the PROCESSES parameter. When the listener believes the current number of connections has reached maximum load, it may set the state of the service handler for an instance to "blocked" and begin refusing incoming client connections with the error:

TNS-12516 TNS:listener could not find instance with matching protocol stack

Solution
To implement the solution, please execute the following steps to increase the number processes and sessions:

1) Connect to the XE database using the sys or system user:
sqlplus system/
2) To confirm the PROCESSES and SESSIONS values, run the following script:
sql> col name format A30
sql> col value format A30
sql> select name, value from v$parameter where name in ('processes','sessions');
3) SQL> alter system set processes=300 scope=spfile;
4) SQL> alter system set sessions=300 scope=spfile;
5) Bounce the database to reflect the changes
6) To confirm new values run the script (2).