Subsystem Details:

Creating a Subsystem Description

You can create a subsystem description in two ways. You can copy an existing

subsystem description and change it, or you can create an entirely new description.

The following are two approaches you can use:

v Copying an existing subsystem description

1. Create a duplicate object, CRTDUPOBJ, of an existing subsystem

description. (You can also use the WRKOBJ or WRKOBJPDM commands.)

2. Change the copy of the subsystem description.

See Appendix C. IBM-Supplied Object Contents, for examples.

v Creating an entirely new subsystem description

1. Create a subsystem description (CRTSBSD).

2. Create a job description (CRTJOBD).

3. Add work entries to the subsystem description.

a. ADDWSE (Add workstation entry)

b. ADDJOBQE (Add job queue entry)

c. ADDCMNE (Add communications entry)

d. ADDAJE (Add autostart job entry)

e. ADDPJE (Add prestart job entry)

4. Create a class (CRTCLS).

5. Add routing entries to the subsystem description (ADDRTGE).

Starting a Subsystem

To start a subsystem, use the Start Subsystem (STRSBS) command or the Work

with Subsystem Description (WRKSBSD) command. To use the STRSBS

command, specify the following:

STRSBS SBSD (SBSD=library/subsystem

description name)

For example

STRSBS MYLIB/MYSTORE

How a Subsystem Starts

When a subsystem starts, the system allocates several items and starts autostart

and prestart jobs before it is ready for work.

1. After the Start Subsystem (STRSBS) command is issued, the system allocates

the following items, finding the information in the subsystem description:

v Pools of main storage

v Display stations

v Communications devices

v Job queues

2. Next, the autostart jobs and prestart jobs are started and the subsystem is

ready for work. Figure 3 shows what occurs when a subsystem starts.

Chapter 4. Subsystems 83

Subsystem Monitor Job

The subsystem monitor job provides control over an active subsystem. It provides

functions such as initiating, controlling, and ending jobs. Several subsystem monitor

jobs may run on a system at any given time.

Subsystem monitor jobs are identified by type SBS on the Work with Active Jobs

display. You can see this by using the Work with Active Jobs (WRKACTJOB)

command.

Note: IBM supplies two complete controlling subsystem configurations: QBASE

(the default controlling subsystem), and QCTL. Only one controlling

subsystem can be active on the system at one time. The Controlling

Subsystem Description (QCTLSBSD) system value determines

Electronics Hobbyist

Follow some interesting embedded system projects in the below hobbyist link.

http://blog.vinu.co.in/

some electronics related blogs where we can learn more ..

http://arshad-umar.blogspot.in/

http://mihirknows.blogspot.in/2012/06/fixed-error-occurred-while-gathering.html

Android Fundamentals

Before directly going to the application development, I thought its better to read something on the Android OS. It was quite interesting to me when I understand that each applications in this OS is treated as different user with different permissions to the assoicated files.More over this OS runs with Linux Kernal as a multi-user Linux system in which each application is a different user.

•By default, the system assigns each application a unique Linux user ID (the ID is used only by the system and is unknown to the application). The system sets permissions for all the files in an application so that only the user ID assigned to that application can access them.

•Each process has its own virtual machine (VM), so an application's code runs in isolation from other applications.

•By default, every application runs in its own Linux process. Android starts the process when any of the application's components need to be executed, then shuts down the process when it's no longer needed or when the system must recover memory for other applications

•It's possible to arrange for two applications to share the same Linux user ID, in which case they are able to access each other's files. To conserve system resources, applications with the same user ID can also arrange to run in the same Linux process and share the same VM (the applications must also be signed with the same certificate).

•An application can request permission to access device data such as the user's contacts, SMS messages, the mountable storage (SD card), camera, Bluetooth, and more. All application permissions must be granted by the user at install time.

Refer Application Fundamentals