This exit translates predefined hexadecimal strings into nulls in DB2®, and translates a null back to the specified hexadecimal value on retrieval from DB2.
For example, your program could insert either high values or low values in a packed decimal field to represent that a valid field value is not known. In a DB2 application, nulls are often used to represent column values that are not known at insert time.
NULLVAL DC X'FFFFFFF' NULL VALUE
No
other changes to the sample NULLCOL exit are required. The NULLCOL exit should be copied to a new source member with an 8-byte name and the appropriate nulls value specified at the NULLVAL label. The new exit must be assembled and link-edited, and mapped, The mapping is shown in Figure 1:
----------------------------- CICS VT: Update field ----------------------------
Command ===> ________________________________________________ Scroll ===> CSR_
Data set name : ORDERFL
Creator : PROD +
Table : ORDER_TAB +
Data set length: 00352
Field name . . . . . . : VIDF0019
Field length . . . ===> 00004 (In bytes)
Field type . . . . ===> P ("C", "P", "U", "X", "F", "H")
Column name . . . ===> CREATE_DATE................... + (Look-up available)
Starting position ===> 00259 ("1" = Beginning of data set)
Picture or FBE . . ===> EXITL=NULLSMP1____________ (example HH.XX.SS.NNNNNN)
(or MMDDYY)
(or EXITx=exit name)
Parameters . . . . ===> __________________________ Optional user parameters
Special function . ===> ___ ("KEY", "PTH", "BKY", or blank)
Mapped from table ===> P ("P"=Prim, "X"=Not mapped)
Build order . . . ===> 00019 ("1"=first, "2"=second and so on)
Press: Enter=Update PF3=Exit PF1=Help
Note that the exit compares the value of the entire VSAM field to the hard-coded nulls value.