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Running DIFROM to Export Data (12 of 17)

DIFROM Builds Routines Containing Data Dictionaries

Next, DIFROM builds the routines containing the DDs, data, and file security. To save space in the init routines, cross-references are not sent. They are rebuilt when the inits are run on the target system. DDs are turned into routines that hold parts of each data dictionary node on separate lines. The global reference is listed on one line; its value is recorded on the next line. Thus, for each node in the data dictionary there are two corresponding lines in the init routine.

The routine lines that hold data dictionary information begin with two semicolons. This format conforms to the VA programming standard for using $TEXT to reference routine lines. When the data dictionaries are put into place during the init process, the lines are referenced using indirection as follows:

    ^DD(442,0)="value"    becomes      ;;^DD(442,0)

If the "value" is too long to fit on a single line, it is divided between two lines. The first "value" line starts with a tilde (~) and the second with an equal sign (=).

If the installer chooses to update the data dictionaries, data dictionary nodes on the target system are overwritten. This will bring in newly-defined fields, including specifications for cross-references or triggers. It will also replace existing field definitions (data dictionary nodes) with incoming definitions. Thus, revisions of existing fields may occur. However, the process will not alter nodes that exist on the target system but that are not in the incoming data dictionary. For example, if a field has been deleted from the source system's data dictionary, that field will not be deleted on the recipient's system. Instead, a pre-init program can be used to delete obsolete fields and obsolete data dictionary nodes.

If auditing is turned on at the sending site, the DD node indicating that auditing should occur will be sent. In this situation, auditing will be turned on at the installing site if the data dictionaries are updated.


Reviewed/Updated: March 10, 2007