1. Chapter 13
Subsystems

2. Understanding AS/400 System Operations
Basic 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
Understanding AS/400 System Operations

3. Memory: Activity Levels
Activity levels - enhance raw memory allocation by restricting how many programs will vie for the same memory at the same time.
Understanding AS/400 System Operations

4. Why 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
Understanding AS/400 System Operations

5. Understanding AS/400 System Operations
Memory: Storage Pools
A storage pool is a pool of memory where one type of program or application (a set of programs) runs.
Understanding AS/400 System Operations

6. Understanding AS/400 System Operations
Subsystems 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.
Understanding AS/400 System Operations

7. Single Vs. Multiple Subsystem Configuration
Single - QBASE
The subsystem for all work active upon installation
Convenient for installation
Doesn’t take advantage of system’s 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
Understanding AS/400 System Operations

8. Understanding AS/400 System Operations
5 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
Understanding AS/400 System Operations

9. 5 Basic Subsystems (cont.)
QINTER
Subsystem that supports interactive jobs
QSPL
Handles all spooled file jobs
Understanding AS/400 System Operations

10. 5 Basic Subsystems (cont.)
QCMN
Supports all communications jobs
QBATCH
Supports all batch jobs
Understanding AS/400 System Operations

11. 5 Basic Subsystems (cont.)
The AS/400 allows for any combination of jobs within a subsystem. However, doing so will reduce the system’s efficiency.
The object, subsystem description, is required whenever a new subsystem is created.
Understanding AS/400 System Operations

12. Understanding AS/400 System Operations
System 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).
Understanding AS/400 System Operations

13. Storage Pool Characteristics
Activity Level
Max number of jobs that can be run simultaneously in the pool How many lanes
Pre-defined size
number of bytes that can be stored in the pool How much water
Understanding AS/400 System Operations

14. Understanding AS/400 System Operations
Shipped Storage Pools
*MACHINE is the storage pool where the system runs.
*BASE can be where everything else runs.
IBM ships AS/400 with two storage pools.
*Machine
*Base
Understanding AS/400 System Operations

15. Understanding AS/400 System Operations
Related System Values
QMCHPOOL - Sets Size OF *Machine pool.
QBASPOOL - Sets minimum size of *BASE pool.
Understanding AS/400 System Operations

16. Understanding AS/400 System Operations
Portion of Memory
A pool is the amount of allocated memory.
Understanding AS/400 System Operations

17. Memory 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.
Understanding AS/400 System Operations

18. Memory Management Concepts
Timeslice, is the period of time allocated for CPU usage by a job when it executes.
Thrashing is excessive faulting.
Understanding AS/400 System Operations

19. Understanding AS/400 System Operations
CPU 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
Understanding AS/400 System Operations

20. CPU 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
Understanding AS/400 System Operations

21. Understanding AS/400 System Operations
AS/400 Jobs Three States
Active—The job is running. Job is occupying storage, using processor, and hasn’t exceeded activity level.
Wait—The 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 can’t occupy storage or processor due to activity level is at max.
Wait – for some of the following:
Press of Enter Key
File to open/close
Read/Write record
Locked record
Message
Device allocation
Ineligible – waiting to run.
System busy
Time slice is finished – end of allocation time. CPU switched to next job in queue.
Understanding AS/400 System Operations

22. AS/400 Jobs Three States (cont.)
Jobs shift between states automatically, depending on system’s work load
Job may need to become ineligible at end of its time slice
Understanding AS/400 System Operations

23. Understanding AS/400 System Operations
Memory 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.
Understanding AS/400 System Operations

24. Understanding AS/400 System Operations
Pre-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.
*SPOOL—Supports spool writers (printing).
*SHRPOOL1 through *SHRPOOL60— Names available for customer-defined shared pools.
Understanding AS/400 System Operations

25. Creating Private Pools/ Assigning Shared Pools
Create Subsystem Description (CRTSBSD)
Type choices, press Enter.
Subsystem description _______ Name
Library *CURLIB Name, *CURLIB
Storage pools: ___
Pool identifier _________
Storage size _________ Number, *BASE, *NOSTG...
Activity level _______ Number
+ for more values _________
Maximum jobs *NOMAX , *NOMAX
Text 'description' *BLANK   
Bottom
F3=Exit F4=Prompt F5=Refresh F10=Additional parameters F12=Cancel
F13=How to use this display F24=More keys
Figure 13-1: CRTSBSD command screen for memory pool assignments.
Understanding AS/400 System Operations

26. Changing 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)
Understanding AS/400 System Operations

27. Changing 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)
Understanding AS/400 System Operations

28. Table 13-1: Memory Activity Level Commands
Understanding AS/400 System Operations

29. Understanding AS/400 System Operations
CHGSHRPOOL 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
F3=Exit F4=Prompt F5=Refresh F10=Additional parameters F12=Cancel
F13=How to use this display F24=More keys
Figure 13-2: CHGSHRPOOL command
Figure 13-2
Understanding AS/400 System Operations

30. Private Pools Changed Within Subsystems
Change Subsystem Description (CHGSBSD)
Type choices, press Enter.
Subsystem description > QINTER Name
Library *LIBL Name, *LIBL, *CURLIB
Storage pools: __
Pool identifier *SAME , *SAME
Storage size _________ Number, *BASE, *NOSTG...
Activity level _________ Number
+ for more values           
Maximum jobs *SAME , *SAME, *NOMAX
Text 'description' *SAME                                
___________________________________________________________________________
Bottom
F3=Exit F4=Prompt F5=Refresh F10=Additional parameters F12=Cancel
F13=How to use this display F24=More keys
Figure 13-3: CHGSBSD command to change private pool sizes.
Understanding AS/400 System Operations

31. Work with Subsystems (WRKSBS)
Work with System Status
System: BIGBLUE
Type options, press Enter.
4=End subsystem 5=Display subsystem description
8=Work with subsystem jobs Subsystem Pool 1
Subsystem Pool 2
Total Subsystem Pools
Opt Subsystem Storage (K)
_ QBASE
_ QBATCH
_ QCMN
_ QCTL
_ QINTER System Pool 3
_ QCOMPILE System Pool 11
_ QSERVER
_ QSPL
_ QSYSSBSD
_ QSYSWRK System Pool 2
Bottom
Parameters or command
===>_________________________________________________________________
F3=Exit F5=Refresh F11=Display system data F12=Cancel
F14=Work with system status
Figure 13-4: work with subsystems command.
Understanding AS/400 System Operations

32. WRKSBS – Display Pool Definitions
System: BIGBLUE
Subsystem description: QCOMPILE Status: ACTIVE
Pool Storage Activity
ID Size (K) Level
*BASE
*SHRPOOL Shared Pool Names
Subsystem Pool Number
Bottom
Press Enter to continue.
F3=Exit F12=Cancel
Figure 13-5: Command WRKSBS, displaying pool definitions.
Understanding AS/400 System Operations

33. Work with System Status
Work with System Status BIGBLUE
07/05/99 12:06:24
% CPU used : Auxiliary storage:
Elapsed time : 00:30:01 System ASP : M
Jobs in system : % system ASP used . :
% addresses used: Total : M
Permanent : Current unprotect used: M
Temporary : Maximum unprotect . : M
Type changes (if allowed), press Enter.
System Pool Reserved Max DB Non-DB---
Pool Size (K) Size (K) Active Fault Pages Fault Pages
System Pool Number
Bottom
Command
===>___________________________________________________________
F3=Exit F4=Prompt F5=Refresh F9=Retrieve F10=Restart
F11=Display transition data F12=Cancel F24=More keys
Figure 13-6: Command WRKSYSSTS, information about system pools.
Understanding AS/400 System Operations

34. Understanding AS/400 System Operations
Work Shared Pools
Work Shared Pools
System: BIGBLUE
Main storage size (K) . :
Type changes (if allowed), press Enter.
Defined Max Allocated Pool -Paging Option--
Pool Size (K) Active Size (K) ID Defined Current
*MACHINE *FIXED *FIXED
*BASE *FIXED *FIXED
*INTERACT *FIXED *FIXED
*SPOOL *FIXED *FIXED
*SHRPOOL *CALC  *CALC
*SHRPOOL *FIXED *FIXED
*SHRPOOL *CALC  *CALC
*SHRPOOL *FIXED *FIXED
*SHRPOOL *FIXED *FIXED
*SHRPOOL *FIXED
More...
Command
===>____________________________________________________________________
F3=Exit F4=Prompt F5=Refresh F9=Retrieve F11=Display tuning data
F12=Cancel
Figure 13-7: Command WRKSHRPOOL.
Understanding AS/400 System Operations

35. Subsystem Description
Create Subsystem Description (CRTSBSD)
Type choices, press Enter.
Subsystem description NEWSBS Name
Library *CURLIB Name, *CURLIB
Storage pools: _
Pool identifier
Storage size *BASE Number, *BASE, *NOSTG...
Activity level Number
+ for more values         
Maximum jobs , *NOMAX
Text 'description' *BLANK                            
______________________________________________________________________
Additional Parameters
Sign-on display file *QDSIGNON Name, *QDSIGNON
Library ________ Name, *LIBL, *CURLIB
Subsystem library *NONE Name, *NONE
More...
F3=Exit F4=Prompt F5=Refresh F12=Cancel F13=How to use this display
F24=More keys
Figure 13-8: Prompted CRTSBSD command.
Understanding AS/400 System Operations

36. Add Storage Pools to Subsystem
Specify More Values for Parameter POOLS
Type choices, press Enter.
Storage pools:
Pool identifier >
Storage size *BASE Number, *BASE, *NOSTG...
Activity level ________ Number
Pool identifier
Storage size Number, *BASE, *NOSTG...
Activity level Number
Pool identifier
Storage size Number, *BASE, *NOSTG...
Activity level Number
More...
F3=Exit F4=Prompt F5=Refresh F12=Cancel F13=How to use this display
F24=More keys
Figure 13-9: Adding storage pools to a new subsystem description
Understanding AS/400 System Operations

37. Understanding AS/400 System Operations
Routing Entries
Display Job Description
System: BIGBLUE
Job description: QINTER Library: QGPL
Message logging:
Level : 4
Severity : 0
Text : *NOLIST
Log CL program commands : *NO
Accounting code : *USRPRF
Print text : *SYSVAL
Routing data : QCMDI
Figure 13-10: A sample of the routing data for a job description.
Understanding AS/400 System Operations

38. Routing Entries (cont.)
Display Routing Entries
System: BIGBLUE
Subsystem description: QINTER Status: ACTIVE
Type options, press Enter.
5=Display details
Start
Opt Seq Nbr Program Library Compare Value Pos
_ QCMD QSYS 'QCMDI'
_ QCMD QSYS 'QS36MRT'
_ QARDRIVE QSYS '525XTEST'
_ QCL QSYS 'QCMD38'
_ QCMD QSYS *ANY
Bottom
F3=Exit F9=Display all detailed descriptions F12=Cancel
Figure 13-11: Routing entries in the subsystem description.
Understanding AS/400 System Operations

39. Routing Entries (cont.)
Display Routing Entry Detail
System: BIGBLUE
Subsystem description: QINTER Status: ACTIVE
Routing entry sequence number : 10
Program : QCMD
Library : QSYS
Class : QPTY35
Library : QGPL
Maximum active routing steps : *NOMAX
Pool identifier : 2
Compare value : 'QCMDI'
Compare start position : 1
Press Enter to continue.
F3=Exit F12=Cancel F14=Display previous entry
Figure 13-12: Expanded routing entries in the subsystem description.
Understanding AS/400 System Operations

40. Understanding AS/400 System Operations
Workstation Entries
AS/400 workstations are devices (Interactive Jobs Only)
Job Queues
Autostart Jobs
Communication Jobs
Pre-start Jobs
Understanding AS/400 System Operations

41. Understanding AS/400 System Operations
Starting Subsystems
Start Subsystem (STRSBS)
Type choices, press Enter.
Subsystem description Name
Library *LIBL Name, *LIBL, *CURLIB
Bottom
F3=Exit F4=Prompt F5=Refresh F12=Cancel F13=How to use this display
F24=More keys
Figure 13-13: Prompted STRSBS command.
Understanding AS/400 System Operations

42. Understanding AS/400 System Operations
Ending Subsystems
End Subsystem (ENDSBS)
Type choices, press Enter.
Subsystem > QBATCH Name, *ALL
How to end *CNTRLD *CNTRLD, *IMMED
Delay time, if *CNTRLD *NOLIMIT Seconds, *NOLIMIT
Bottom
F3=Exit F4=Prompt 5=Refresh F10=Additional parameters F12=Cancel
F13=How to use this display F24=More keys
Figure 13-14: Prompted ENDSBS command.
Understanding AS/400 System Operations

43. Basic Work Management Structure
System
Subsystem
Job
Routing Step
System Values
Description
Work
Entries
Routing
Class
Program
Understanding AS/400 System Operations

44. Understanding AS/400 System Operations