Jes Material

Programme on IBM S/390

Scope of Discussion  What is JES  Types of JES and their function  Phases of Job Processing  JES2 Parameters  JES Spool and Spool Datasets  JES2 Start Options  JES2 Shutdown

…contd    

JES2 Security JES Messages and their resolution JES2 Commands Question-Answer Session

What is JES  JES is a subsystem which MVS uses to receive jobs into the OS, schedule them for processing and to control their processing  Simply stated, JES is that component of MVS that provides necessary function to get jobs into, and output out of, the MVS system

Types of JES  JES may be of two types : - JES2 - JES3  JES2 provides the functions of a job entry system in a uniplex environment  JES3 provides the functions of a job entry system in multiplex environment

Phases of Job Processing      

Input Phase Conversion Phase Processing Phase Output Phase Hard-Copy Phase Purge Phase

Concept of Internal Readers  MVS uses Internal Readers to pass to JES2 the JCL for started tasks, START command, and TSO LOGON request  An internal reader is a program that other programs can use to submit jobs and commands to JES2.  JES2 can receive multiple jobs thru multiple internal readers  Internal reader types : INRDR,TSOINRDR,STCINRDR

Input Phase  JES2 reads input stream, assigns jobid to each job, and places each job’s JCL , optional JES2 control statements onto DASD datasets called Spool Datasets.  JES2 then selects jobs from spool datasets for processing and subsequent processing (concept of spooling)

Conversion Phase  JES2 uses a converter program to analyze each job’s JCL and changes it into converter/interpreter test(CI text)  CI text understood by JES2 and scheduler function of MVS  CI text put on the spool dataset  In case of JCL errors, the job queued for output processing and not execution

Processing Phase  JES2 selects job from job queue and pass on the same to MVS Initiators -- An initiator is a system program that starts a job to allow it to compete for system resources with other jobs  Initiator selects jobs on the basis of PGN, PRTY, JOB classes  The initiator allocates the resources specified in the JCL for the first step of the job  The allocation of resources before

Output Phase  JES2 controls all system-produced output including system messages as well as datasets requested by user that must be printed  JES2 groups datasets with similar characteristics  JES2 queues output for print processing

Hard Copy and Purge Phase  After output phase, the output undergoes hard copy phase  After processing the output for a job, JES2 puts the job on the purge queue  Purging is nothing but the deletion of a job and its associated messages from spool datasets

JES2 Initialization Parameters  JES2 initialization parms are stored in the system parameter library and the start-up procedure stored in system procedure library  The initparm contains : checkpoint defn spool def,initiator def,job priority setting printer def,output class def,SMF logging internal reader definition

JES Spool and Spool Datasets  Spool refers to the direct access device that contains the spool dataset. Spool provides simultaneous processing and a temporary storage area for work that is not yet completed.  JES2 writes the job, its JCL, its control statements, and its data to spool dataset until further processing can occur

JES2 Start-up Options JES2 start-up option,in general,can be : - format / noformat : spool vol formatted - Cold / warm : all job purged and all job data on the spool volume scratched  In case of cold or format option, the JES2 goes for cold start  In case of format option, JES2 formats all existing spool volumes.Otherwise, JES2 formats any unformatted spool vol

 The warm start of JES2 is the recommended as well as the safest option with no inherent risk. It is possible only if previous shutdown was normal

JES2 Shutdown JES2 shutdown should be performed only after all the subsystems have been stopped. JES2 is shut using the following cmd : $P JES2 or $PJES2 Danger !!! : The JES2 shutdown command should not be given except during the system shutdown process or else result may be totally un-predictable

JES2 Security JES2 Security is ensured by Resource Access and Control Facility (RACF) The JES2 resources are spool, job queue, purge queue, execution queue The RACF resource class/group where JES security definitions are made is JESSPOOL and GSDSF

JES2 Messages JES2 messages have a common format : all start with the prefix $HASP which stands for Houston Automatic Spooling Priority. The JES2 message format : ssid hh.mm.ss jobid @/b/+/square $haspnnn text + : indicates no operator action required b : blank, if no operator action required @ : indicates operator action by JES2 gen module square : indicates a request for operator action

JES2 Commands The common JES2 commands are : $d xxx display commands $t xxxx change command $s xxxx start command $c xxxx cancel command $p xxxx purge command

JES2 Commands $n xxxx repeat printer command $b xxxx backspace printer command $i xxxx interrupt printer command $f xxxx advance printer command $e xxxx restart printer command $z xxxx halt printer command