This issues was faced by a developer, who asked for the solution, so here is something can be done at database level -
[a]
Create an Oracle profile and limit the number of sessions per database user, for example:

sql> CREATE PROFILE <profilename> limit SESSIONS_PER_USER 1;
sql> ALTER USER <username> <profilename>;
sql> ALTER SYSTEM SET RESOURCE_LIMIT=TRUE;
Using this approach, please be aware that dead connections will not always be detected by the database immediately, so users might occasionally not be able to login even a single time until a database administrator has killed their session. Also, …