Before z/OS release 1.12, there was a special DB2 image that contained all the conversions used worldwide by DB2. This support was not needed after release 1.7 and its support for dynamic loading was removed in release 1.12.

Beginning with z/OS release 1.7, you do not need to be concerned that the DB2 pre-built image is not being loaded. This is because z/OS Unicode Services now loads conversions the first time they are requested automatically or "on demand". The system starts with an empty z/OS Unicode environment and z/OS Unicode Services loads conversions as needed. This "on demand" feature makes the DB2 pre-built image unnecessary. You can see that your conversions are being loaded by issuing the MVS command DISPLAY UNI,CONV.

Changes in z/OS release 1.9 make it much more likely that the DB2 pre-built image will not be loaded. Specifically, the C Run-time function iconv() was changed to use z/OS Unicode Services to perform its conversions. If this function is used before DB2 starts, then the DB2 pre-built image is not loaded. Unicode on demand will load conversions as needed. Many programs use the iconv() functions and so it is likely one of these may call iconv before DB2 is started.