(1).
EXEC SQL
INCLUDE CUSTDCL
END-EXEC.
(2).
EXEC SQL
COPY CUSTDCL
END-EXEC.
INCLUDE is executed at pre-compile time (by the SQL Compiler).
COPY is executed at compile time (by COBOL Compiler).
WRONG:
(2) We can use COPY for DCLGEN, but get RC=4 from precompiler because the pre-compiler searchs for the host variables used in SQL statement and it doesn't not find them returns 4.