Wednesday, January 28, 2015

Context and Context Free Servers

Context free servers/Services: Servers(Services) that don't save the information about previous request is referred as Context free servers.

Servers that save the information about previous request as a reference for a subsequent request are called Context Servers.

Various components of Pathway subsystem

Process: Any running program is called process. Each time a program is executed, operating system creates a process. If two different programs are executed, 2 processes will be created. If single program is executed by two different users concurrently, OS will create 2 processes.

PATHMON: is a Pathway monitoring process. It supervises all the processes in the pathway environment. Only one PATHMON process will be there for any Pathway.

PATHCOM: is a command line interface, which allow system operators to communicates with PATHMON to control the processes.

SCREEN COBOL Library: Contains the requesters programs after they are compiled by SCOBOLX compiler, which means all the requester screens objects will be present in SCL.

TCP(Terminal Control Process):
 

What is IPCs??

IPCs -- Inter Process Communication messages commonly known as IPCs. Requesters and Servers communicate each other through IPCs.

There are 2 types of IPCs messages:
1. Request 2. Reply

Request Messages:

Request Messages are sent from a Requester and received by particular Service of the SERVER.

Commonly Request messages are initiated from SCREEN COBOL with SEND statement. Pathway then routes the request to a server containing the service. Server then reads the message using special file $RECEIVE.

Reply Messages:

Reply messages are formatted by SERVICE and sent back to the requester after the service is completed. Reply message is written to $RECEIVE and pathway routes this information to requester.

Reply message contains the requested information if the service is successful or error message if the service is not successful.

Source: HP PathMaker Manual
 

What is SERVER ??

A server is a database management program, written in a programming language
such as COBOL85, TAL, C. PATHMAKER generates servers in COBOL85 or C.

What is Requester??


Requesters are mostly written in SCREEN COBOL, a high-level language similar to COBOL and designed specifically to create Pathway requester programs. Once coded, the requester is translated into pseudocode (using the SCOBOLX compiler) and is then stored in a SCREEN COBOL library.

 

What is OLTP??

OLTP stands for Online Transaction Processing.

The approach used for Pathway applications involves dividing the application into two parts: one to perform data collection and the other to access and modify the data. The application programs that perform these two roles are known as the requester and the server.

Requesters and servers communicate with inter-process communication (IPC) messages. 

What is PATHWAY??

Pathway is a Tandem product that supplies the tools and environment that assist in the creation and running of OLTP applications.
 
Pathway is mainly used to
1. Develop applications based on server-requester model
2. Running Requester-Server based application.
 
 

 

Saturday, January 17, 2015

PATHWAY Notes

PATHMON

PATHMON is a monitoring process that defines and manages server objects and -if your environment includes Pathway/iTS – TCPs, TERM objects and program objects. Each PATHMON environment includes only one PATHMON process.

PATHCOM

PATHCOM is command line interactive interface to communicate with PATHMON process. As an alternative to using PATHCOM, management application program can be written.

SERVER Object

Definitions of server classes is called SERVER object. Server class is multiple copies are SERVER programs. Executing Server program is called SERVER process.

LINKMON

LINKMON is process that manages communication between PATHSEND process and SERVER Classes. PATHSEND processes are user application which use PATHSEND procedure calls to send requests to SERVER classes.
Note: Above objects and processes are provided by Nonstop TS/MP.

TCP objects

Terminal control process that runs screen(SCREEN COBOL) programs and coordinate communication between screen programs, input-output devices or processes, server processes and the PATHMON processes.

TERM Objects

Definitions of tasks that uses screen programs to control input-output devices such as terminals and workstations.

Program object:

Templates for creating and starting temporary TERM objects. Above objects and processes are provided by the Pathway/iTS product.

System Management Tools:

We can use one of two ways to configure and control PATHMON-controlled objects in Pathway.
1.    Interactively, by entering commands
2.    Programmatically, by writing a management application program.

Interacting with PATHMON:

Interactive way

PATHCOM $PPX (PATHMON process name)

6:56:34 (qdev) $AUDIT.C997240 14> PATHCOM $PPX
$X7CY: PATHCOM - T0845H09 - (01JUL13)
(C)2008-2013 Hewlett Packard Development Company, L.P.

Non-interactive way

IN-COMMAND
PATHCOM /IN PWCMD, OUT $S.#LP, CPU 1, NOWAIT/ $PMX

OBEY Command:
>>PATHCOM $PMX
>> OBEY PWCMD

TACL Routines: TACL inline facility allow us to interact with PATHMON in non-interactive way.
USING defines:
12>ADD DEFINE =CMD-FILE, CLASS MAP, FILE $DATA.PW.CONFIG
13> ADD DEFINE =OUT-FILE, CLASS SPOOL,LOC $S, REPORT “CONFIG”
14> PATHCOM/IN =CMD-FILE, OUT =OUT-FILE/ $PMX

Configuring Global parameters

SET PATHWAY command is used to define the limits for your overall configuration and to specify node-independent, owner and security attributes.

Specifying Limits:
Limits are global values that determine the maximum number of objects of each type that you can define when you are ready to configure individual objects. For example, suppose that you suppose that you want to indicate that your system will permit a maximum of:

  • 5 server classes
  • 25 server processes
  • 5 server STARTUP messages
  • 7 server ASSIGN messages
  • 5 server PARAM messages

To establish these limits, you can use these commands.

= SET PATHWAY MAXSERVERCLASSES 5
= SET PATHWAY MAXSERVERPROCESSES 25
= SET PATHWAY MAXSTARTUPS 5
= SET PATHWAY MAXASSIGNS 7
= SET PATHWAY MAXPARAMS 5

PATHMON process save the configuration details in the memory until you start the PATHMON process. After starting PATHMON process it will write to PATHMON configuration file.

Specifying Owner and Security Attributes:

This section will be updated .. if you have any notes regarding any HP NonStop topic please share with us ..