Unload/reload gives the following abend:
UT004008 ***ERROR*** - REQUIRED LOAD SUBSCHEMA/DMCL/DATABASE NAME PARAMETER MISSING
Release : All supported releases.
Component : CA IDMS
Incorrect SEGMENT specification
The UT004008 message in the documentation is rather cryptic.
The most common cause of this error is that an SQL defined database is being unloaded and the old and new segments in the input are not the same.
When running unload/reload on an SQL defined database, the old and new segments must be the same.
This is documented at \UNLOAD\Parameters under reload-segment-name.
This error can also be issued for NON-SQL database if the Segment for the Unload/Reload is not found in the RELOAD DMCL
When running unload/reload, the easiest way to manage the required database definition entities is to use a permanently maintained "new" DMCL for the purposes of describing the new physical database characteristics.
Before the unload/reload, make the necessary changes to the segment definition and re-compile the new DMCL. At this point, the old DMCL load module (the live one used at run-time) still contains the old physical characteristics and it is the old and new DMCL load modules that unload/reload loads and uses.
After the unload/reload is complete, re-compile the live DMCL. No source changes should be required at this point.
This method can be used for both network- and SQL-defined databases, but is mandatory for SQL-defined databases.
It is described in more detail in KD 24632: What are the steps to run a basic unload-reload? (Steps 6 and 7).