The ALWNULL keyword on CTL-OPT (or H-spec) controls how SQL NULL values in
database columns are handled by native file I/O (CHAIN, READ, WRITE, UPDATE).
| Value | Behaviour |
|---|---|
*NO (default) |
Reading a record containing a NULL raises the data-mapping I/O error, %STATUS 01299 |
*INPUTONLY / *YES |
NULLs read silently as type defaults (blanks / zero); writes always store values |
*USRCTL |
%NULLIND(field) is maintained on read and honored on WRITE/UPDATE (an on indicator stores SQL NULL) |
CTL-OPT ALWNULL(*USRCTL);
See the Disk File I/O chapter for the full read/write semantics and an example.