Tivoli Service Desk 6.0 Developer's Toolkit Interface Designer Guide
EHLLAPI (Emulator High Level Language Application Programming Interface) is an API supplied by IBM Communications Manager (IBM CM/2). Its function is to allow an application to interact with the screen of a mainframe by sending commands to the emulator card in a workstation.
Interacting means that an application can:
Essentially, EHLLAPI allows an application to do anything that a user can do with a host terminal emulation window.
Mainframe applications often use proprietary database formats for which there is no API. This means that the only way to access data is through the application's user interface screens. Therefore, the only route for an automated interface to such an application is EHLLAPI.
For applications that do provide APIs, some mainframe programming expertise is required to access them. An EHLLAPI interface requires no mainframe programming and the workstation programming it does require is straightforward.
Because an EHLLAPI application is controlled from a local workstation, support center personnel can start it, stop it, and monitor it without having to work through a mainframe.
Following are the minimum requirements to run EHLLAPI. We suggest a Pentium processor with 16 MB RAM, but the following configuration is acceptable:
EHLLAPI for TSD Developer's Toolkit adds support for EHLLAPI into the TSD Script programming language. This means that TSD Script has built-in commands that make direct calls to the API. Additionally, there are several high level commands which make programming EHLLAPI easier than programming with other EHLLAPI packages.
Another advantage of EHLLAPI is that you program in the same language in which an application is written. This means, for instance, that direct calls from Tivoli Problem Management (TPM) code to EHLLAPI routines are seamless. Your EHLLAPI routine has access to the full complement of TSD Developer's Toolkit capabilities, including windowing and SQL commands.
There are several models for EHLLAPI use:
If you want to set up EHLLAPI routines that perform tasks that a user would normally do with the host, then you implement automated utilities. These are routines that are called directly from a Tivoli Systems application and that execute on a user's machine. In other words, each LAN workstation has its own link to the host.
As an example, there may be a TPM solution that requires a terminal to be recycled. Without EHLLAPI routines, the user can do the following:
With EHLLAPI, you can create a routine that does the following:
This routine can be called anywhere in TPM, or run as a stand-alone routine from an icon on each machine. Users only need to make sure that a terminal session is started in the Communications Manager.
EHLLAPI can be used as an interface between a host application and Tivoli Systems databases. For this model, a dedicated LAN workstation is loaded with TSD Script programs that execute on an interval basis. These programs re-synchronize the databases by uploading and downloading the most recent data.
As an example, you might need an interface between TPM's problem database and IBM's InfoMan product because only your first level support personnel use TPM.
EHLLAPI programs must be written to carry out the upload/download process with InfoMan. The programs include the logic involved in identifying problems that should be transferred.
This model fits in cases where all data records need to be transferred between systems, as well as in cases where only data that fits a specific criteria is transferred.
Because all the EHLLAPI code is placed on one OS/2 machine, the rest of the machines can also run OS/2.
Batch mode occurs when programs are executed by a scheduler. This means that programs are executed on a scheduled interval.
Downloading is the process of moving data from a host computer to a local workstation.
Input inhibition occurs when a mainframe cannot accept input from a user. In that case, the system displays an X (for 3270) or II (for 5250) in the Operator Information Area (OIA). This indicates that no keyboard input is accepted until the X disappears.
Map entries are a single line in the Fields section of a map file which relates one TSD Script record field to one host field.
Map files are text files which describe the relationship between TSD Script variables and a host screen. A map file consists of a Header section and a Fields section. For more information, see "Map Files and the Map Utility."
A map upload occurs when the TSD Script Interpreter uses a map file to take the values from a given TSD Script variable (or record variable) and place them in the host screen.
A map download occurs when the TSD Script Interpreter uses a map file to read data from the host screen and place it in the given TSD Script variable (or record variable).
The Operator Information Area (OIA) is the bar at the bottom of the terminal window which displays status indicators to the user. Status indicators include:
Sessions occur when more than one terminal emulation window is opened with the Communications Manager at a time. Each terminal window is known as a session with the host.
Session names are "short names" which are letters of the alphabet. For instance, one session on your machine may be named 'A', while another may be 'B.'
Terminal window is equivalent to a session, as used in this book.
Uploading occurs when data is sent to a host computer from a local workstation.
A watch is the name of the process whereby an application waits for a certain condition to occur on the host, such as the input inhibited indicator to disappear, or a string to appear. There are specific EHLLAPI commands to execute these watches.
The EHLLAPI installation can be run either as a:
To install EHLLAPI as a standalone application requires a previously successful TSD Developer's Toolkit installation.
The following procedure allows you to install EHLLAPI as a supplemental product during the TSD Developer's Toolkit installation.
Tivoli Service Desk 6.0 Developer's Toolkit Legacy APIs Guide