Altering IMS database mapping cases and fields within it using DDL

Based on the current IMS ALTER TABLE syntax documentation, there is currently no way to add a single mapping case or to drop a single mapping case at the moment. You can only drop the complete mapping definition and add it again including the additional mapping case, which should be added, or without the mapping case, which should be deleted. This is hard to do with complex mappings consisting of a large amount of cases. There is currently also no way to add a field to an existing mapping case than to drop the whole mapping and add it again, which is also hard to with complex mappings consisting of a large amount of mappings or even single mappings with lots of fields within it.

To simplify the modification of IMS database mapping definitions, please add an ALTER MAP map_name option to the ALTER TABLE statement with suboptions ADD CASE case_id AS case_name (column_definitions), ALTER CASE case_name (add_alter_or_drop_column_declarations) and DROP CASE case_name. It could potentially be more intuitive to reference a mapping case in a different way when adding, altering or dropping colums, which are part of a mapping case. For instance ALTER TABLE table_name IN DATABASE database_name ALTER COLUMN column_name IN MAP map_name CASE case_name column_alteration_definitions is probably be more intiutive to use than ALTER TABLE table_name IN DATABASE database_name ALTER MAP map_name ALTER CASE case_name ALTER COLUMN column_name column_alteration_definitions. The challenge with the first is, that the keyword IN is already being used with ARRAYs an STRUCTs, which can be also a part of a mapping case. This could be solved by adding the ARRAY or STRUCT name as last part of such an IN clause: ALTER TABLE table_name IN DATABASE database_name ALTER COLUMN column_name IN MAP map_name CASE case_name array_or_struct_name column_alteration_definitions. Another way could be the dot notation you are using with the COMMENT ON statements: ALTER TABLE table_name IN DATABASE database_name ALTER COLUMN map_name.case_name.column_name column_alteration_definitions respectively with ARRAY or STRUCT fields: ALTER TABLE table_name IN DATABASE database_name ALTER COLUMN map_name.case_name.array_or_struct_name.column_name column_alteration_definitions but you should consistently use dot notation and/or IN notation throughout all statements. The dot notation has the problem, that you are concatenating potentially very long names, which makes it hard, where you have for instance a line limitation to 80 characters like when executing the SQL Batch Utility or a potential future native DDL utility.