Start profile defines which SAP services are started -- for example, message server, dialog, gateway or enqueue process. The startsap program is responsible for starting these service processes, and it uses a start profile to begin the startup process. The default profile is used if you want to assign the same parameter value for all application servers (such as the name of the database host, or the host on which the message server is running). Instance profiles provide an application server with additional configuration parameters to complement the settings values from the default profile.
Typically, these parameter settings adapt the instance according to the desired resources. They also define the available instance resources -- main memory, shared memory, roll memory and so on -- and how to allocate memory to the SAP application buffers.
M FAROOQ Ali
SAP BASIS/ BI Consultant
This was first published in November 2006