Device dependent support
Device dependent support (DDS) is an installation feature that enables device-dependent maps.
When you assemble your map sets, you specify the type of terminal the maps are for in the TERM option. This causes the assembler to store the physical map set under the MAPSET name suffixed by the character for that type of terminal. You also can use JCL or the link-edit NAME statement to control the member name under which a map set is stored. When you issue SEND MAP or RECEIVE MAP with DDS active, BMS adds a 1-character suffix to the name you supply in the MAPSET option. It chooses the suffix based on the definition of your terminal, and thus loads the physical map that corresponds to the terminal for any given execution.
BMS defines the suffixes used for the common terminal types. A 3270 Model 2 with a screen size of 24 rows and 80 columns is assigned the letter 'M,' for example. The type is determined from the TYPETERM definition if it is one of the standard types shown in Table 1.
| Code | Terminal or logical unit |
|---|---|
| A | CRLP (card reader input, line printer output) |
| B | Magnetic tape |
| C | Sequential disk |
| D | TWX Model 33/35 |
| E | 1050 |
| F | 2740-1, 2740-2 (without buffer receive) |
| G | 2741 |
| H | 2740-2 (with buffer receive) |
| I | 2770 |
| J | 2780 |
| K | 3780 |
| L | 3270-1 displays (40-character width) |
| M | 3270-2 displays (80-character width), LU type 2s |
| N | 3270-1 printers |
| O | 3270-2 printers, LU type 3s |
| P | All interactive LUs, 3767/3770 Interpreter LU, 3790 full function LU, SCS printer LU |
| Q | 2980 Models 1 and 2 |
| R | 2980 Model 4 |
| U | 3600 (3601) LU |
| V | 3650 Host Conversational (3653) LU |
| W | 3650 Interpreter LU |
| X | 3650 Host Conversational (3270) LU |
| Y | 3770 Batch LU, 3770 and 3790 batch data interchange LUs, LU type 4s |
| blank | 3270-2 (default if TERM omitted) |
An installation can also define additional terminal types, such as the miniature screen previously described. The system programmer does this by assigning an identifier to the terminal type and specifying it in the ALTSUFFIX option of the TYPETERM definition for the terminals. When you create a map for such a terminal, you specify this identifier in the SUFFIX option, instead of using the TERM option. Transactions using the map must also point to a PROFILE that specifies alternate screen size, so that ALTSUFFIX is used.
- BMS adds the ALTSUFFIX value in the terminal definition to your map set name, provided that definition specifies both ALTSUFFIX and ALTSCREEN, and provided that the screen size for the transaction is the alternate size (either because the transaction PROFILE calls for alternate size, or because the default and alternate sizes are the same).
- If these conditions are not met, or if BMS cannot find a map with that suffix, it attempts to find one with the suffix that corresponds to the terminal type in the terminal definition.
- If BMS cannot find that map either, it looks for one with no suffix. (A blank suffix indicates an all-purpose map, suitable for any terminal that might use it.)
Device-dependent support is an installation option for BMS, set by the system programmer in the system initialization table. Be sure that it is included in your system before taking advantage of it; you should know whether it is present, even if you are supporting only one device type.
With DDS in the system, there is an efficiency advantage in creating suffixed map sets, even if you are supporting only one device type, because you prevent BMS from attempting to load a map set that does not exist before defaulting to the universal one (the blank suffix).
Without DDS, on the other hand, it is unnecessary to suffix your maps, because BMS looks for the universal suffix (a blank) and fails to locate suffixed maps.