SDF cannot be used unless a basic system syntax file is present. The basic system syntax file is activated automatically when the system is loaded. Further system syntax files - the subsystem syntax files - may be present in addition to the basic system syntax file.
Only one basic system syntax file can be active in the entire system at any given time.
Entries on system syntax files are maintained in the SDF parameter file. The system syntax files are managed by the systems support staff by means of the MODIFY-SDF-
PARAMETERS command. The SDF-PAR utility routine allows the systems support staff to create an SDF parameter file.
Basic system syntax file
The basic syntax file contains the definitions of the application areas, the standard statements and the SDF-specific commands (from the SDF application area) as well as the system-wide global information settings. The SYSSDF.SDF.210 syntax file is activated for this purpose by default. Systems support can make modifications with the SDF-A or SDF-U utility routines (e.g. to restrict functions). Modifications apply to all users of the system. Exchanging the basic system syntax file during the session takes immediate effect for all existing and future tasks.
Subsystem syntax file
There can be also several subsystem syntax files activated in addition to the basic syntax file. A subsystem syntax file contains the definitions of commands and programs that belong to a subsystem managed by DSSM or even to any installation unit (including
BS2CP). Subsystem syntax files can be modified using SDF-A. Any such modifications, e.g. limitations on functional scope, apply for all users of the system.
Exchanging a subsystem syntax file during the session takes immediate effect for all existing and future tasks.
There are two ways to activate subsystem syntax files:
Tthe name of the subsystem syntax file is defined in the subsystem declaration. In this case, the subsystem syntax file is automatically activated when the subsystem is loaded and deactivated when the subsystem is unloaded.
The name of the subsystem syntax file is entered in the SDF parameter file. In this case, the subsystem syntax file is automatically activated at system initialization. If the pubset on which this file is stored is not available when the system is initialized, then it can only be activated after importing the pubset.
It can be modified (deactivated or exchanged) via the SDF parameter file only. In this case, the subsystem syntax file is available independently of the availability of the corresponding subsystem.
If a command or statement definition is defined in more than one active subsystem syntax files, then the following cases arise:
Only one version of the subsystem can be active at a time. In this case the command or statement definition is used that is found in the syntax file of the version of the subsystem last activated.
Several versions of the subsystem can be active at a time (coexistence). The following cases arise:
The command or statement definition from the syntax file of the corresponding subsystem version is used for a task that is assigned to a specific subsystem version.
The syntax analysis of a START-<utility> command is always performed before the program is loaded, i.e. before connecting the task to a subsystem version of the program called. This is why the syntax file of the first version of the subsystem activated is evaluated.The command or statement definition contained in the first version of the subsystem activated is used for tasks that are not assigned to any subsystem version.