One of the most asked question in a SAP interview is whether it is possible to have a self defined transaction code in SAP. The answer to the question is simple and if given tactfully can impress the interviewers.
To start with, yes, self-defined reports, transactions or functions are possible within SAP. There might be numerous reasons why a company might go in for customized transaction codes or for that matter reports. To cater to this demand, SAP allows creation of user-defined transaction codes.
Creating a transaction code allows the user to speed up access to specific reports/programs as the user no longer needs to use transaction code [SA38]. Thus, instead of using T-Code SA38, then entering the program name or report name and pressing execute, the same can be done directly through a pre-defined T-Code. The user can then simply use a transaction code, which will automatically open the program. In SAP custmoized T-codes can be created through transaction code [SE93].