Oracle Forms

Hi,
In Forms 10G on when-new-form-instance I can specify:
:B1.user_name := user.
The word user turns "blue" after I key it so I assume it's an special reserved word in Forms.
This statement will fetch the user id of the person executing the program.
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I need to find out what SID the program is running in.
The same program is running in different SIDs and depending upon the SID, there is special
conditioning the program needs to do.
I tried: :B1.SID_NAME = sid , but that didn't work. Looks like 'sid' is not a special name like 'user' is.
How can I set up forms to have "sid" work like "user", or how to I query it from system tables?
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We have one application server which contains only this copy of this forms program. When the user
logs onto the system using a log in form we use, the user specifies which (database) server they want to
log on to, but all use the same application server. It's the SID of this database server they log onto that I need
to determine in the forms program.
Thanks
Sandy