Can you start SAP without ASCS ?
Most of you will call it a lame question and would say NO.
But its not true !!!
I started SAP App server without ASCS and it came up.
I was also able to login to it with sap* / pass.
Now, question is how could it happen.
I checked profile files and for ASCS profile file no information ab't DB is provided, even in the fresh installation of NW too.
I would request experts to pitch in and throw some light on it.
Amit Bangotra replied
What you are saying is true, but is also infact wrong.
ASCS is a totally separate entity from application server (PAS) ,
ASCS only provides enqueue and message service and they don't need any connection to database to function. Message server is required for SAP load balancing in case of multiple application servers and load distribution and enqueue service used by SAP to implement its own locking mechanism independent of database which manages the SAP lock table. ( SM12 Tcode)
Both ASCS and application server can be started and stopped independently .
But SAP will not work without ASCS, you might be able to login but will not be able to do any updates or change anything without enqueue server and get errors that lock management is not available and also that message server is not available.