By default, the product is installed using the SOLIS procedure. In turn, this requires the IMON installation monitor. EDT V17.0 can no longer be used in systems in which IMON is not present.
In existing programs which call EDT via the L mode subroutine interface, the library name $EDTLIB is present as a fixed program element. This type of program can only work with EDT V17.0 in compatibility mode. To ensure that these programs can continue to run unchanged, it is either necessary to save a copy of the library SYSLNK.EDT.170 under the name $TSOS.EDTLIB or make a corresponding entry in the global system alias catalog (see manual Guide to Systems Support [13] section ACS: Alias catalog system).
The REP file SYSREP.EDT.170 must be shareable (USER-ACCESS=SPECIAL). Only then are the corrections loaded on the dynamic loading of EDT.
For performance reasons, it is also possible to load EDT as a subsystem (see below).
Start procedure: EDTSTART
For each publicly installed EDT version, IMON can be used to install an EDT start procedure which is valid for all user IDs. The installation location of the procedure file can be chosen freely as required (see also the section on the EDT start procedure). The logical identification SYSDAT.EDTSTART is defined for this file in the SYSSII file.
The /SET-INSTALLATION-PATH command can be used to inform the installation monitor of the installation file name. EDT retrieves this information using the IMON function GETINSP and the defined path is set instead of $.EDTSTART. If no file is assigned to the logical ID SYSDAT.EDTSTART then EDT uses the EDT start procedure $.EDTSTART if this exists.
EDT as subsystem
EDT consists of three subsystems: EDTCON, EDTU and EDT. All the EDT subsystems run independently of the addressing mode, i.e. they can run with 24-bit or 31-bit addressing. The decision whether to load a subsystem into the upper or lower address space therefore depends on the addressing mode applicable to the most frequent users of the EDT subroutine interface.
The EDTCON subsystem (which consists of the modules EDTCON, IEDTGLE and EDTSSLNK) is loaded into the lower address space. In EDT V17.0A, EDTCON is simply an adapter which supplies the previous EDT entries in compatible form and dynamically loads its own initialization module IEDTCRT from the library SYSLNK.EDT.170.INIT into the user's address space. However, the EDTCON module is no longer supplied as an OM but as an LLM.
The EDTU and/or EDT subsystems can be loaded into the upper address space. The EDTU subsystem contains the modules which are required for EDT to run in Unicode mode, while the EDT subsystem contains the equivalent modules for compatibility mode. Depending on the intended type of utilization, it may make sense to preload only one of the two subsystems. When the operating mode is switched, the other subsystem would then be dynamically loaded as a private copy. However, it is only possible to preload these two subsystems if the EDTCON subsystem has already been preloaded.
If EDT is to run as a main program or subroutine in 24-bit addressing mode then either the IEDTCRT module establishes a connection to an EDT system loaded in the lower address space or EDT is dynamically loaded privately in the lower address space.
The mechanism for switching between the EDT operating modes is also implemented in IEDTCRT. This means that depending on whether EDT is called as a main program via /START-EDTU or /START-EDT or, equally, on the employed version of the subroutine
interface, processing branches either to the EDTU subsystem (Unicode mode) or the EDT subsystem (compatibility mode). IEDTCRT functions are also used when the operating mode is changed explicitly or implicitly due to user input.
The EDTCON subsystem can be preloaded with
/START-SUBSYSTEM SUBSYSTEM-NAME=EDTCON,SYNC=*YES
It is then possible to start the subsystems EDTU and/or EDT using
/START-SUBSYSTEM SUBSYSTEM-NAME=EDTU
or
/START-SUBSYSTEM SUBSYSTEM-NAME=EDT
in any desired order.