Autoinstall for terminal definitions
General-use programming interface
This chapter describes autoinstallation of terminal resource definitions.
- “How autoinstall terminal identifiers are generated”
- “Defining an autoinstall model terminal using masking”
- “Using an autoinstall control program”
- “Writing your own autoinstall program”
– “Autoinstalling terminal definitions”
– “Deleting autoinstalled terminal definitions”
CICS needs a TCT definition for each terminal device with which it communicates. However, a CICS/400 system may have many connected terminals, and there is a great deal of keying work associated with creating individual TCT entries for each terminal. Because many of your terminals have identical properties, you can use the autoinstall facility to reduce the number of TCT definitions you have to create. Instead of a TCT entry for each terminal, you create a model TCT definition that could apply to many terminals of the same type. When you log on from a terminal, CICS/400 uses the model to create dynamically an entry for that terminal in the TCT. The terminal identifier is generated by CICS/400 from the OS/400 device description information contained in the SIT. This process is referred to as terminal masking.
Optionally, you can specify a CICS program to be called by CICS/400 to generate a terminal identifier. This program is referred to as an autoinstall control program. CICS/400 calls the program referenced by the AEGTCACP PPT entry defined to the control region, after the terminal masking process has completed.
With autoinstall, the amount of storage required for terminal definitions is reduced. Definitions are installed when they are needed, that is when the user logs on from the terminal.
Definitions are deleted when the user has logged off, and the autoinstall inactivity limit has expired. The autoinstall inactivity limit is specified in the DEVCTL parameter of the SIT.
Autoinstall models may be created for 3270 displays, including those with the double-byte capability, 5250 displays, and ASCII terminals. The DEVMODEL parameter of the TCT is used to indicate whether the definition can be used as a model terminal resource definition.
Client terminals are a special case of autoinstalled terminals. While able to take advantage of autoinstall model terminal definitions, they also possess some unique characteristics.
- Client terminal installation is driven by the internal transaction CTIN. This is invoked by CICS client external presentation interface (EPI) applications to install a remote-terminal entry in the CICS control region.
- The client-terminal identifier is not defined using the SIT mask and AEGTCACP exit program described in this chapter. It is generated automatically by the CTIN transaction.
- Client terminals are deleted either by a CTIN uninstall request issued by the client EPI application, or by a CCIN install request for a client that is already installed.
The CICS Client INstall transaction (CCIN) and CICS Terminal INstall transaction (CTIN) can be found in group AEGCLI.
Figure . Flowchart of the autoinstall functions
How autoinstall terminal identifiers are generated
CICS/400 offers two ways of generating autoinstall terminal resource definitions. If, when the user attempts to log on at the terminal, no TCT definition is found for the terminal, one of the following may happen:
- If an AEGTCACP PPT entry is not defined to the control region, CICS/400 uses the masking facilities defined in the SIT to generate a terminal identifier.
- If an AEGTCACP PPT entry is properly defined to the control region, CICS/400 first uses the masking facilities to generate a potential terminal identifier.CICS/400 then calls the autoinstall control program referenced by the AEGTCACP PPT entry. Assuming a successful return from the autoinstall control program, CICS/400 uses the terminal identifier returned from thatprogram.
The use of an autoinstall control program is optional; by default, masking is used to autoinstall terminals. If you wish to use an autoinstall control program, you must supply an AEGTCACP PPT entry for it.