HP 3000 Manuals HP 3000 Manuals
Access Server Program Flow
Access PC and Access Server use interprocess communication (IPC) to give
PC users access to host and remote data.
Datacomm Connections
The PC-to-host connection can be either of two types:
* Using HP OfficeShare PC network software on the PC and HP
OfficeShare LAN/3000 software on the host.
NOTE For the specific datacomm configurations Access Server supports in
the HP OfficeShare PC networking environment, please contact your
HP representative.
* Over an RS-232/422 hardwired, X.25, or modem connection using the
basic serial software that is part of Information Access. This
supports a direct connection to an Advanced Terminal Processor
(ATP) on a Series 3X through 7X host or a Distributed Terminal
Controller (DTC) on a Series 9XX host.
Startup Sequence
The various options available for starting the MPE session are described
below and summarized in Table 1-1. (For information about access to
Access Server for users running an MPE interface program such as HP Menu,
see Chapter 12, "PC User Interaction with the Host HP 3000," in the
Information Access Server: Database Administration manual.)
NOTE For basic serial connections, all PCs must be configured as
terminal type 10 through the MPE configuration or by including
;TERM=10 in the logon command. Sessions initiated through the
Remote Connection screen in Access PC are always started as
terminal type 10. PC users with a modem connection to the host HP
3000 may need to be reminded of this.
* In an HP OfficeShare networking environment, an MPE session is
established from the Remote Connection screen by choosing Remote
Connect from the Main Menu in Access PC.
Or, if the PC user chooses Remote Tables, Config Options and a
remote configuration option, or a remote command file, the Remote
Connection screen is automatically displayed to allow the user to
establish the connection.
* In a basic serial environment, PC users connected over a modem or
X.25 connection can connect to MPE and obtain the colon prompt (in
terminal mode or with a terminal emulator such as AdvanceLink)
before starting Access PC, or create a connection file that can be
invoked from the Remote Connection screen. These users can then
log on from the Remote Connection screen by entering their logon
string and passwords or the name of the connection file and its
password. Basic serial connection files are command files that
instruct the PC to perform each step of the connection process to
log the user on or off the HP 3000 through a basic serial
connection. (For more information, see the Using Basic Serial
Connection Files manual.)
PC users working over a hardwired basic serial RS-232/422
connection can establish the MPE session either before starting
Access PC or from the Remote Connection screen in Access PC by
entering their logon string and password. (When a user
establishes the MPE session before starting Access PC, that
session remains active after the user logs off Access PC.)
They could also use a simple logon file to establish the session
from the Remote Connection screen. Simple logon files contain the
:HELLO command used with the users' logon string, and for HP
OfficeShare, a SERVER command.
In a basic serial environment, PC users may override their
existing MPE sessions when they use the Remote Connection screen
to start a new session. In an HP OfficeShare environment, a
session created before starting Access PC (using a terminal
emulator such as AdvanceLink) remains active. However, the
session cannot be affected or controlled through Access PC.
NOTE When the host session is established from the PC, the MPE user
identified in the logon sequence must have IA and SF capabilities
in order to use Access Server. To use the Host Batch Facility, the
MPE user must also have BA capability; saving result tables as
saved tables, however, does not require BA capability. ND
capability is needed to be able to create the spoolfile that would
record any serious errors that might occur while the user is
active.
Table 1-1. Establishing MPE Sessions
-----------------------------------------------------------------------------------------------------
| | | | | |
| Network | Log on before | Type logon at the | Use connection | Use simple logon |
| connection | running | Remote Connection | file at the | file from the |
| | Information | screen | Remote Connection | Remote Connection |
| | Access | | screen | screen |
| | | | | |
-----------------------------------------------------------------------------------------------------
| | | | | |
| Basic serial | Yes | Yes, if | Yes. A previous | No |
| modem, | | intermediate | session may be | |
| multiplexer, or | | datacomm | terminated, or if | |
| X.25 | | connection is | the connection | |
| | | already | file is set to | |
| | | established. | test for an | |
| | | | existing session, | |
| | | | the session can | |
| | | | be continued | |
| | | | without | |
| | | | interruption. | |
| | | | | |
-----------------------------------------------------------------------------------------------------
| | | | | |
| Basic serial | Yes | Yes. Any | Yes, but not | Yes |
| hardwired | | previous session | usually | |
| | | is automatically | necessary. A | |
| | | terminated. | previous session | |
| | | | can be terminated | |
| | | | or continued | |
| | | | without | |
| | | | interruption, | |
| | | | depending on the | |
| | | | file commands. | |
| | | | | |
-----------------------------------------------------------------------------------------------------
| | | | | |
| HP OfficeShare | No | Yes | No | Yes |
| network | | | | |
| | | | | |
-----------------------------------------------------------------------------------------------------
The following startup sequence is followed each time a PC user starts
Access Server:
1. The PC user runs Access PC and establishes an MPE session on the
host HP 3000 at the Remote Connection screen, or a session is
established before starting Access PC.
2. At the Remote Connection screen, the user enters an Access Server
user name and password or names a connection file.
3. The user requests data via the Remote Tables function, and PC
datacomm software sends the request to the host.
4. In a basic serial environment, a datacomm interface program
(PCSERVER.PUB.SYS) is run on the host when the host receives the
PC's first transmission.
In an HP OfficeShare environment, the interface process
HDSPNS.PPC.SYS is created when the user provides the information
needed to start the MPE session. HDSPNS creates the session in
response to the Access PC request for a session environment. It
then adopts itself into the session.
5. The interface process (PCSERVER or HDSPNS) creates a "son" server
process called the Host Data Server Process (HDSP.PPC.SYS). Figure
1-2 illustrates this PC-to-host interaction.
The interface process also creates two temporary IPC files used
during data transmission:
* LINK0002 holds host-to-PC transmission data written by HDSP
in response to PC requests. This data is stored until
PCSERVER or HDSPNS reads it.
* LINK0003 holds PC-to-host data written by PCSERVER or
HDSPNS and stored until HDSP reads the requests.
![[]](../../pic3k/M012036/FFN23c50.gif)
Figure 1-2. Access PC/Access Server Interaction
6. The HDSP checks the Access Server enable flag; if it is not set,
the HDSP returns the following message to the PC:
Information Access Server has not been made available to users
(AC5018)
The enable flag is set when you or the primary DBA use the UDC
ENABLEAC or run the Administrator Utility with PARM=1 to make
Access Server available to users. The user OPERATOR can also
enable or disable Access Server (but cannot use any other
functions in the Administrator Utility). For more information,
see "Enabling Access Server" in Chapter 4, "Access Server
Operations."
If the flag is set and Access Server is available, the PC/host
interface is complete.
NOTE This explanation of PC-to-host communication holds true for each PC
logged on to Access Server. For each PC running Access Server, the
following are created on the host:
* An MPE session (unless an existing basic serial connection
is used).
* A PCSERVER process or an HDSPNS process.
* Two IPC files called LINK0002 and LINK0003.
* The Host Data Server Process (HDSP).
* One or two spoolfiles for each user session. The spoolfile
HDSPERR records serious errors with the HDSP server process;
the spoolfile HDSPNSE records serious errors with the HDSPNS
server process in the HP OfficeShare networking environment.
If no errors occur, the spoolfile is deleted when the
session terminates. If serious errors occur, a record of
the error messages is written to the spoolfile.
Operation
When the PC/host interface is complete, Access Server is ready to receive
and process PC users' data requests. The Access PC/Access Server program
flow is illustrated in Figure 1-3.
Access Server decodes each request received, retrieves the requested data
from the appropriate data source, formats it into tables, and returns it
to the PC via the HDSP (and PCSERVER or HDSPNS) in data packets
appropriate to the transaction type.
* If the requested data resides on a remote HP 3000, the HDSP opens
a datacomm connection (NS/3000) to that system. This connection
remains open until the user exits from Information Access.
Each time the user requests data from the remote HP 3000, the HDSP
checks to see if the connection is still open. If it is not, the
HDSP logically closes it and then reopens it.
If the connection can't be reopened, the HDSP returns an error
message to the PC.
The PC receives the transmission and routes it to Access PC. The
requested data is displayed on the PC screen.
Co-processing is now initiated between Access PC and Access Server. The
two applications operate interactively, transferring data between the PC
and the host.
Entries in the Information Access data dictionary are used to interpret
and validate requests. The data is formatted into tables and returned to
the PC via the HDSP and the server process.
![[]](../../pic3k/M012036/FFN33c50.gif)
Figure 1-3. Access PC/Access Server Program Flow
Termination
When the PC user exits from Access PC, the server processes are no longer
required. Both the HDSP and the server process for that PC are
terminated (unless the host session was established prior to running
Access PC).