System administration may modify the command and statement definitions provided by Fujitsu, either system-globally (system syntax files) or specifically for individual users (group or user syntax file). Any system-global modification that has been made can be retracted specifically for particular users (by means of entries in the group syntax files).
As of SDF-A V3.0, each user has access to the full range of SDF-A functions. While enabling the user to process group and system syntax files (taking due account of file attributes and privileges), this does not allow the user to activate group and system syntax files. System syntax files can be activated for systems and group syntax files for user IDs only at the discretion of system administration. For example, the user can generate a group syntax file with modified command definitions. System administration can then take this group syntax file generated by the user and assign it to a user ID such that it will be activated when the SET-LOGON-PARAMETERS command is processed.
The definitions provided by Fujitsu for commands implemented via system modules may be modified only so long as the modification does not affect the functional scope of the command. For example, a user may change the default value of an operand but not the data type of a value defined for that operand.
A modification often involves a number of individual but coordinated steps. If a certain modification is used repeatedly, it is advisable to write a modification procedure containing all the SDF-A statements needed to modify a command or a statement. These procedures can then be used to update the group and user syntax files every time a new version of a product is supplied.
The bulk of this chapter consists of examples illustrating the mode of operation and facilities of SDF-A. Grouped together at the end of the chapter are some general remarks on defining and removing functional limitations.