If you do not have access to the Adaptive Server error log, do not use login triggers. Always check the Adaptive Server error log for error messages.
A client application, like isql, is unaware of the existence or execution of a login trigger; it presents a command prompt immediately after the successful login, though Adaptive Server does not execute any commands before the login trigger successfully executes. This isql prompt displays even if the login trigger has terminated the user connection.
The user logging in to Adaptive Server must have execute permission to use the login trigger stored procedure. If no execute permission has been granted, an error message appears in the Adaptive Server error log and the user connection closes immediately (though isql still shows a command prompt).
Adaptive Server error log shows a message similar to the following:
EXECUTE permission denied on object my_proc, database my_db, owner dbo
The login trigger stored procedure must not contain parameters without specified default values. If parameters without default values appear in the stored procedure, the login trigger fails and an error similar to the following appears in the Adaptive Server error log:
Procedure my_proc expects parameter @param1, which was not supplied...