Session 2724SHARE Summer 2008Peter KaniaJES Product TeamPoughkeepsie, NYkania@us.ibm.com

JES3 Overview for Users and Sysprogs

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Notes:Performance is in Internal Throughput Rate (ITR) ratio based on measurements and projections using standard IBM benchmarks in a controlled environment. The actual throughput that any user wil l experience will vary depending upon considerations such as the amount of multiprogramming in the user's job stream, the I/O configuration, the storage configuration, and the workload processed. Therefore, no assurance can be g iven that an individual user will achieve throughput improvements equivalent to the performance ratios stated here. IBM hardware products are manufactured from new parts, or new and serviceable used parts. Regardless, our warranty terms apply.All customer examples cited or described in this presentation are presented as illustrations of the manner in which som e customers have used IBM products and the results they may have achieved. Actual environmental costs and performance characteristics will vary depending on individual customer confi gurations and conditions.This publication was produced in the United States. IBM may not offer the products, services or features discussed in this document in other countries, and the information may be subject to c hange without notice. Consult your local IBM business contact for information on the product or services available in your area.All statements regarding IBM's future direction and intent are s ubject to change or withdrawal without notice, and represent goa ls and objectives only.Information about non-IBM products is obtained from the manufacturers of those products or their published announcements . IBM has not tested those products and cannot confirm the performance, compatibility, or any other claims related to non-IBM products. Questions on the capabilities of non-IBM products should be addressed to the suppliers of those products.Prices subject to change without notice. Contact your IBM representative or Business Partner for the most current pricing in your geography.

Trademarks

eServer, IBM, IBMLink, InfoPrint, MVS, OS/390, Redbooks, Redbooks (logo), RETAIN, z/OS, zSeries

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JES3 Characteristics

• Centralized management (Global)

• Manages its external store – spool• Stores job control information• Job data• Non-volatile, medium-term buffering of data

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JES3 Characteristics

• Centralized resource management• Systems• Devices & Data Volumes• Jobs

• Workflow Management• In conjunction with z/OS Workload Manager

• Controls available to• Sysprogs (Inish statements, commands, utilities, exits, code modifications)• Operators (commands, utilities)• Application Programmers (JECL statements)

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JES3 Characteristics

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JES3 Phases – Input

• Jobs accepted from various sources• Internal (INTRDR)• External

• Card reader (your grandfather’s, not with your pictures)• Network (NJE,RJP)

• Supported protocols: TCP/IP, BSC, SNA

• Job assigned a job number

• Control blocks created and saved on spool

• Job passed on to the next phase

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JES3 Phases – Conversion

• The job’s JCL (Job Control Language) is converted to internal text and control blocks by the z/OS Converter Interpreter component

• JES3 uses the output to determine resource requirements• MDS (Main Device Scheduling – MDS)

• When all resources are available, the job is made ready for the execution phase

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JES3 Phases – Execution

• JES3 supplies jobs to z/OS Initiators

• Initiators are either JES3- or WLM-managed• If JES3-managed, JES3 controls the number of initiators• If WLM-managed, WLM controls the initiators

• Single-threaded execution• Job must complete before another one can start• Resource unavailability may cause jobs to wait

• Spool buffers the input and output data for the jobs

• When a job finishes, it continues to the Output Processing phase

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JES3 Phases – Output

• Output processing function keeps track of all available data andschedules writers to process it

• Matches output requests from output functions with available output• A data base consisting of OSEs (Output Service Elements)• Additional control structures maintained for faster access

• Master OSEs (MOSE)• Scheduler elements (OSS)• Summary tables (OST)

• Provides output to external functions• SAPI (Sysout API)

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JES3 Phases – Writer processing

• Writers• JES-managed

• Local• Remote

• External writers• Applications (SAPI)

• Dynamic and Hot writers

• JES3 and FSS writers

• Network writers

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JES3 Phases – Purge

• All traces of a job removed from JES3• Control blocks removed• Job number made available• Spool space returned back to the pool

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JES3 Complex

• Global• Centralizes control of the whole complex• Single point of failure

• Dynamic System Interchange (DSI) addresses that

• Locals• Depend on the global for their function

• JESXCF• Communication vehicle used by the global and the locals• Separate component• Limited use by JES2 as well

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Functional Subsystems

• Provide a function outside of the JES3 address space• More distributed load• Function offload

• Usually common to JES2 and JES3• AFP (advanced function printing)• Converter/Interpreter (CI) FSS – only used in JES3

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JES3 as the primary subsystem

• Other components make requests to JES3 via Subsystem Interface, e.g.:• Job Select• Data set allocation• Output selection for processing

• Primary Subsystem:• First in line• Other subsystems are ‘Secondary’

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Spool Datasets and Checkpoint

• Spool used for• Control information

• Jobs• Other structures not directly related to a specific job

• Input and output data• Short-term in nature• Shared by all systems in the JES3 complex• Data set to z/OS• ‘No data integrity’ set for the data set!• Cannot be moved

• Checkpoint used for• System status information (Complex Status Record)• (Spool) Volume information• Etc.

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Job Control Table

• Always the first ‘spool extent’

• Size determines the maximum number of jobs

• Keeps track of all jobs in the system• Each record mapped by the JCT (IATYJCT) macro• Root for other job-related control blocks, e.g.:

• JDS – Job Data Set control block – directory of all Sysin and Sysout files• OSE – Output Service Element• Etc.

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JES3 Job Flow

• 4 standard job phases• Converter/Interpreter• Main• Output Service• Purge

• JES3 allows for non-standard jobs• E.g. a called Dynamic Support Program (DSP) - Display

• Display• Purge

• Note the absence of Output Service• Output collected under ‘Job zero’

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Converter Interpreter

• Input: Job’s JCL

• Output: MVS Scheduler control blocks

• JES3 scans for resource requirements• Device set up information: Devices and volumes needed• Preliminary tables built for the Main phase• User exits available to inspect the data

• Can run as a subtask on the Global

• Can be offloaded to a C/I FSS address space

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Main

• Main Device Scheduling• Updates the tables built by C/I• Works with DFSms to determine device and volume placement• Matches available resources to jobs

• Limits jobs to systems where resource are available• Stops jobs from starting executions when resources not available• Operator commands to make a volume unavailable

• Device fencing• Devices made available to only certain classes

• Generalized Main Scheduling• Uses job class groups• 255 job classes (up to 8 characters)• Uses limits defined in the inish statements

• Applicable to the complex or a single system

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OUTSERV Scheduler Element

• Prepares the job’s output for output processing

• Schedules output writers• Dynamic writers (start automatically when output available)• Hot writers (started by a command)• Dynamic hot writers – start automatically, stop after a timeout• JES3 vs. FSS writers• BSC/NJE ‘writers’

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Output Services

• Services application requests for output• SAPI – Sysout API• SNA/NJE via BDT• InfoPrint writers

• Keep track of processed/unprocessed output

• When all output is processed, the job is allowed to go to the next phase …

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Purge Processing

• Removes all traces of the job from the system• Returns all resources back to the (s)pool• Cuts an SMF record (SMF 6)• JCT marked available