HP 3000 Manuals HP 3000 Manuals
Display Screen Ownership
When you use IMF/3000, you need not be aware of who owns the display
screen at any particular time. With SNA IMF, however, knowing who owns
the display screen at a particular time can help you determine the state
of your session and which keys or commands you should enter.
IMF/3000
To use IMF/3000, you do not need to be aware of who owns the display
screen.
SNA IMF
To use SNA IMF, you need to be aware of how screen ownership is handled.
A session is the logical connection between Network Addressable Units
(NAUs). Three types of NAU sessions exist: SSCP-PU, SSCP-LU, and LU-LU.
During session initiation, display screen ownership passes through three
stages: (1) unowned; (2) owned by an SSCP-LU session; and (3) owned by
the LU-LU session.
For example, if you are using the Time Sharing Option (TSO), you will
receive four different types of screens before completing your logon to
the host:
1. An unowned screen.After the first RECV3270 intrinsic call, you
receive an unowned screen that contains the SNA IMF banner. Send
the SYS REQ key now. Sending the SYS REQ key affects screen
ownership. Sending the SYS REQ key also clears the screen image
and sets the cursor to the top of the screen.
2. A blank SSCP screen. This screen appears after the SYS REQ key is
sent. The blank screen is produced internally by SNA IMF. Screen
ownership switches to the SSCP-LU session. After receiving this
screen, enter your logon to the host.
3. An LU-LU owned BIND screen.The host receives this screen after TSO
determines that your LU will be permitted to start a TSO session.
4. An unowned screen. This screen is produced by SNA IMF whenever an
UNBINDis received. TSO sends a BIND-UNBIND-BIND sequence when
establishing a session. The unowned screen appears immediately
after the SSCP-LU BIND screen and before your TSO session is
created.
5. An LU-LU owned screen.This screen contains three items: logon
messages from the host, an indication of whether logon was
successful, and the READY message.
NOTE Sending the SYS REQ key
while using a full screen-oriented application destroys the
integrity of your screen image. Once this happens, the host
application must recover the screen image.
Table D-1 lists the three states of display screen ownership, what each
state means, and how you can change display screen ownership.
Table D-1. Display Screen Ownership
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| |
| Display screen Meaning How to change screen ownership |
| ownership |
| |
| Unowned You have either just opened a Send the SYS REQ key to transfer |
| device for SNA IMF communication screen ownership to the SSCP-LU |
| or just logged off the host. session if you have just opened a |
| device. |
| |
| Owned by You have sent the SYS REQ key, If there is no LU-LU session, send |
| anSSCP-LU session which changes the screen ownership the SYS REQ key to make the screen |
| from unowned (the previous screen) unowned. If an LU-LU session |
| to SSCP-LU ownership (the current exists, send the SYS REQ key to |
| screen). You can now log on to transfer screen ownership back to |
| the system. the LU-LU session. |
| |
| Owned by anLU-LU An SSCP-LU session was the owner Either send the SYS REQ key to |
| session of the previous screen. Logon was transfer screen ownership to the |
| completed successfully. SSCP-LU session or log off to make |
| the screen unowned. |
| |
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The display screen is unowned when a device is first opened for SNA IMF
communication.
The SSCP-LU session enables you to create an LU-LU session, which allows
communication between two end users (application programs, devices, or
people). Once you enter the logon message followed by the SYS REQ key,
the newly created LU-LU session allows you to exchange data with the IBM
host through 3270-type screen images.
When a terminal receives a BINDfrom the host, the terminal's screen is
put into an LU-LU session. Receipt of an UNBINDfrom the host puts the
screen into an unowned state.