As mentioned in Chapter 3, Domino 7 introduces the ability to use IBM DB2 as a data store. To support this, four new DB2-related @Functions have been added. These include @IsDB2, @DB2Schema, @IsEmbeddedInsideWCT, and @PolicyIsFieldLocked.
@IsDB2 lets you query a database to determine whether it is a DB2-backed Domino database. It provides two signatures; the first is a server and filename, and the second is a server and a replica ID. This is useful for preventing runtime errors in cases where you might not fully know which servers your code will run against. This function is particularly important if a database is replicated between a standard NSF-based Domino server and a DB2-backed Domino server.
@IsDB2 returns a 1 if the Domino database is backed by DB2 and returns a 0 if it is not. This function can be combined with @DbName to test the current database for DB2 support. @IsDB2("" : "") is equivalent to the use of @DbName.