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Subsystems

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Subsystems

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    1. 1 Chapter 13 Subsystems

    2. Understanding AS/400 System Operations 2 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.

    3. 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.

    4. 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

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

    6. Understanding AS/400 System Operations 6 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.

    7. 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

    8. Understanding AS/400 System Operations 8 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

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

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

    11. 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.

    12. Understanding AS/400 System Operations 12 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).

    13. 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

    14. Understanding AS/400 System Operations 14 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 IBM ships AS/400 with two storage pools. *Machine *Base

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

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

    17. 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.

    18. 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.

    19. Understanding AS/400 System Operations 19 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

    20. 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

    21. Understanding AS/400 System Operations 21 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. 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.

    22. 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

    23. Understanding AS/400 System Operations 23 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.

    24. Understanding AS/400 System Operations 24 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.

    25. Understanding AS/400 System Operations 25 Creating Private Pools/ Assigning Shared Pools Figure 13-1: CRTSBSD command screen for memory pool assignments.Figure 13-1: CRTSBSD command screen for memory pool assignments.

    26. 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)

    27. 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)

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

    29. Understanding AS/400 System Operations 29 CHGSHRPOOL command Figure 13-2Figure 13-2

    30. Understanding AS/400 System Operations 30 Private Pools Changed Within Subsystems

    31. Understanding AS/400 System Operations 31 Work with Subsystems (WRKSBS) Figure 13-4: work with subsystems command. Figure 13-4: work with subsystems command.

    32. Understanding AS/400 System Operations 32 WRKSBS – Display Pool Definitions

    33. Understanding AS/400 System Operations 33 Work with System Status

    34. Understanding AS/400 System Operations 34 Work Shared Pools

    35. Understanding AS/400 System Operations 35 Subsystem Description

    36. Understanding AS/400 System Operations 36 Add Storage Pools to Subsystem

    37. Understanding AS/400 System Operations 37 Routing Entries

    38. Understanding AS/400 System Operations 38 Routing Entries (cont.)

    39. Understanding AS/400 System Operations 39 Routing Entries (cont.)

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

    41. Understanding AS/400 System Operations 41 Starting Subsystems

    42. Understanding AS/400 System Operations 42 Ending Subsystems

    43. Understanding AS/400 System Operations 43 Basic Work Management Structure

    44. Understanding AS/400 System Operations 44

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