Another option that I use on an every day basis is Proxy Authentication.
Provided your TNS alias is MYDB and different usernames are Scott, Joe, and Susy, we could:
1. authorize those users to connect through scott (let's make him a connection user):
alter user joe grant connect through scott;
alter user susy grant connect through scott;
2. create one entry for scott:
mkstore -wrl c:\oracle\wallet -createCredential MYDB scott tiger
3. connect using that entry utilizing proxy authentication:
Auditing can be set up for those proxy connections, so that usual connections as Joe and Susy would not be audited, but when Proxy Authentication is utilized auditing kicks in. It may come in handy when those Joe and Susy some application users of a high-load/chatty application.