The need to have the same password for Apps and Applsys is because when you sign on to apps, initially it connects to a public schema called APPLSYSPUB. This validates AOL username and password that we enter (operations/welcome using guest user account.

Once this is verified we select responsibility, this is validated by APPLSYS schema and then it connects to APPS schema.

Since it uses both applsys and apps during sign on process this expects both the password to be identical.

Try changing apps password to something else and try to login, the validation at the last stage would fail.

This would result in failure of application login. Apps is a universal schema has synonyms to all base product tables and sequences.

This also has code objects for all products (triggers, views, packages, synonyms etc.).

Applsys schema has applications technology layer products like FND and AD etc.