Initializing the output map

Before you start building your output, make sure that the map storage is initialized to nulls, so that data that remains there by a previous process is not used inadvertently.

About this task

If you have read input data using this same map, or one that overlays it, you need to ensure that you have processed or saved this data first. The relationship between input and output maps is discussed in The symbolic input map, and using the same map you used for input is discussed in Sending mapped output after mapped input.

You initialize by moving nulls (X'00') into the structure. The symbolic map structures are defined so that you can refer to the whole map area named the map suffixed by the letter O. You can see this in Figure 3, and, in fact, the following statement would clear the area in which we built the map in the “quick check” example.

 MOVE LOW-VALUES TO QCKMAPO.

If you are using the map for both input and output, it might be easier to clear the map one field at a time, as you edit the input (see Handling input errors).

When you obtain map storage with a CICS® GETMAIN instruction, another way to initialize is to use the INITIMG option.