Title: Subsystems
1Chapter 13
2Basic Facts
- All work is carried out in a subsystem.
- All jobs are divided by type into subsystems.
- Subsystems are started when the AS/400 powers up
and loads the Operating System. - A way of organizing, in order to increase
efficiency.
OFFICE
J O B S
3Memory Activity Levels
- Activity levels -enhance raw memory allocation
by restricting how many programs will vie for the
same memory at the same time.
4Why limit activity level?
- Each job secures enough resources to run
efficiently - Too large of a number will force jobs to compete
for system resources and ultimately slow
completion of all jobs
5Memory Storage Pools
- A storage pool is a pool of memory where one
type of program or application (a set of
programs) runs.
6Subsystems Are
- A subsystem is an environment unique to a type of
program. It allows computer run-time attributes
to be applied to all jobs within it, while other
jobs in other subsystems keep their own
attributes.
7Single Vs. Multiple Subsystem Configuration
- Single - QBASE
- The subsystem for all work active upon
installation - Convenient for installation
- Doesnt take advantage of systems capabilities
- Multiple
- Improves performance to separate workload
- AS/400 comes preloaded with basic 5 subsystems
- Change system value for QCTLSBSD to QCTL the
AS/400 understands to start using multiple
subsystems
85 Basic Subsystems
- QCTL
- the controlling subsystem in a multiple subsystem
configuration - The system console is attached to this subsystem
- This is so the system console can carry out
functions during IPL
95 Basic Subsystems (cont.)
- QINTER
- Subsystem that supports interactive jobs
- QSPL
- Handles all spooled file jobs
105 Basic Subsystems (cont.)
- QCMN
- Supports all communications jobs
- QBATCH
- Supports all batch jobs
115 Basic Subsystems (cont.)
- The AS/400 allows for any combination of jobs
within a subsystem. However, doing so will
reduce the systems efficiency. - The object, subsystem description, is required
whenever a new subsystem is created.
12System Pools
- Also called a storage pool.
- A logical division of main memory reserved for
processing jobs. - Subsystems are pre-assigned to main memory pools
by the Operating System. - Work is divided into types of jobs (Just like
types of pools).
13Storage Pool Characteristics
- Activity Level
- Max number of jobs that can be run simultaneously
in the poolHow many lanes
- Pre-defined size
- number of bytes that can be stored in the pool
How much water
14Shipped Storage Pools
- MACHINE is the storage pool where the system
runs. - BASE can be where everything else runs.
15Related System Values
- QMCHPOOL - Sets Size OF Machine pool.
- QBASPOOL - Sets minimum size of BASE pool.
16Portion of Memory
- A pool is the amount of allocated memory.
17Memory Management Concepts
- Paging is writing a inactive memory page to DASD
so an active page can be read into memory. - Faulting is when a program (or its data) attempts
to access a page not in memory. It then is
fetched.
18Memory Management Concepts
- Timeslice, is the period of time allocated for
CPU usage by a job when it executes. - Thrashing is excessive faulting.
19CPU Considerations
- Time Slices
- The amount of processor time a job has before the
CPU moves to another job - Run Priorities
- Within a storage pool, job with highest prior
acquires system resources first - Ex Print writers, then interactive jobs, then
batch jobs
20CPU Considerations (cont.)
- Run Priority Vs. Job Priority
- Run priority is the priority of job while
executing - Job priority is the relative order of job waiting
on job queue
21AS/400 Jobs Three States
- ActiveThe job is running. Job is occupying
storage, using processor, and hasnt exceeded
activity level. - WaitThe job is waiting for something to happen.
Waiting until next user request to start. - Ineligible The job is ready to run, but the
system is not available. Ineligible job cant
occupy storage or processor due to activity level
is at max.
22AS/400 Jobs Three States (cont.)
- Jobs shift between states automatically,
depending on systems work load - Job may need to become ineligible at end of its
time slice
23Memory Pool Types
- Shared Pools
- Special shared pools. The two pools that come
with the AS/400, MACHINE and BASE, are special
shared pools. These are the only special shared
pools. - General shared pools.
- Private Pools
- Maximum pools 64 including BASE and MACHINE.
24Pre-defined Pools
- The AS/400 comes with predetermined names and, in
two cases, predetermined uses, for shared pools. - Here is the list
- INTERACT Supports interactive subsystems jobs.
- SPOOLSupports spool writers (printing).
- SHRPOOL1 through SHRPOOL60 Names available for
customer-defined shared pools.
25Creating Private Pools/ Assigning Shared Pools
Create Subsystem Description
(CRTSBSD) Type choices, press Enter.
Subsystem description . . . . . _______
Name Library . . . . . . . . . . .
CURLIB Name, CURLIB Storage pools
___ Pool identifier . . . . . .
. _________ 1-10 Storage size . . . . .
. . . . _________ Number, BASE, NOSTG...
Activity level . . . . . . . . _______
Number for more values
_________ Maximum jobs . . . . . . . . . .
NOMAX 0-1000, NOMAX Text 'description'
. . . . . . . BLANK
Bottom F3Exit F4Prompt F5Refresh
F10Additional parameters F12Cancel
F13How to use this display F24More keys
26Changing Pool Memory/ Activity Levels
- Three commands that change memory and activity
level settings on pools. - They are
- Work with System Status (WRKSYSSTS)
- Change Subsystem Description (CHGSBSD)
- Change Shared Pool (CHGSHRPOOL)
27Changing Pool Memory/ Activity Levels (cont.)
- There are also two system values that affect
memory pools and activity levels - Machine Pool (QMCHPOOL)
- Base Activity Level (QBASACTLVL)
28Table 13-1 Memory Activity Level Commands
29CHGSHRPOOL command
Change Shared Storage Pool
(CHGSHRPOOL)
Type choices, press Enter.
Pool identifier . . .
. . . . . __________ MACHINE, BASE,
INTERACT... Storage size . . . . . . . . . .
SAME Number, SAME, NOSTG
Activity level . . . . . . . . . SAME
Number, SAME Paging option .
. . . . . . . . SAME SAME, FIXED,
CALC Text 'description' . . . . . . .
SAME
__________________________________________________
__________________________
Bottom F3Exit F4Prompt F5Refresh
F10Additional parameters F12Cancel
F13How to use this display F24More keys
Figure 13-2 CHGSHRPOOL command
30Private Pools Changed Within Subsystems
Figure 13-3 CHGSBSD command to change private
pool sizes.
31Work with Subsystems (WRKSBS)
32WRKSBS Display Pool Definitions
Figure 13-5 Command WRKSBS, displaying pool
definitions.
33Work with System Status
Figure 13-6 Command WRKSYSSTS, information about
system pools.
34Work Shared Pools
Figure 13-7 Command WRKSHRPOOL.
35Subsystem Description
Figure 13-8 Prompted CRTSBSD command.
36Add Storage Pools to Subsystem
Figure 13-9 Adding storage pools to a new
subsystem description
37Routing Entries
Figure 13-10 A sample of the routing data for a
job description.
38Routing Entries (cont.)
Figure 13-11 Routing entries in the subsystem
description.
39Routing Entries (cont.)
Figure 13-12 Expanded routing entries in the
subsystem description.
40Workstation Entries
- AS/400 workstations are devices (Interactive Jobs
Only) - Job Queues
- Autostart Jobs
- Communication Jobs
- Pre-start Jobs
41Starting Subsystems
Figure 13-13 Prompted STRSBS command.
42Ending Subsystems
Figure 13-14 Prompted ENDSBS command.
43Basic Work Management Structure
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