Increasing simeltaneous connections on oracle XE

If you've set up an oracle server, you may find you need to allow more simeltaneous connections (during heavy testing or data migration for example).

Connect as the system user and issue the following command:
alter system set processes=100 scope=spfile;
where 100 is the number of processes allowed.

You may also want to alter the permissions of the users concerned with the tests:

ALTER USER USERNAME QUOTA UNLIMITED ON USERS;

Where USERNAME is the user's name and USERS is the user's tablespace (default is USERS).
(This information is visible in the SQL section of a user's properties in SQL Developer)