The IMSDBRequester class contains the DL/I calls for the IMS DB. Your program can retrieve, replace, delete, and add segments to the database using the methods in IMSDBRequester. See IMS/ESA Application Programming: DL/I Calls for more information about IMS DB. The class IMSCeldialOrder includes an example of a method that builds a call to an IMS database: the retrieveOrderObjectForKey method creates a database requester and sends it the getUnique: message.
See IMSDBRequester class for a list of the DL/I calls you can make from IMSDBRequester.