Mainframe, MVS and zOS Discussion

Hi,

Why to we use DB2 DCLGEN instead of COPY? Can not that make just same impact?

SQL statements are run through a preprocessor before the COBOL compile is done. The COPY statement is a COBOL verb and hence will not be invoked until the compile, which is after the preprocessor has completed. So using a COPY instead of DCLGEN means nothing will be available to SQL since the preprocessor will not have anything to work with.

Thanks Robert. But if use COPY COPYBOOK with DCLGEN variables, when they will be used by program, program will get them and it will work, right?

The IBM manual at https://www.ibm.com/support/knowledgece ... clgen.html says

The declarations generator (DCLGEN) produces an SQL DECLARE TABLE statement and a COBOL, PL/I, or C data declaration for a table or a view named in the catalog.

So the DCLGEN does the SQL DECLARE TABLE for which the fields can then be referenced in a copy book.