Job Entry Subsystem 1
| Company type | Software subsystem |
|---|---|
| Industry | Computer software |
| Predecessor | MFT |
| Founder | IBM |
| Products | Job scheduling and spooling for OS/VS1 |
Job Entry Subsystem (JES), alternatively referred to as Job Entry Subsystem 1 (JES1), was developed by IBM as a crucial enhancement within OS/VS1, offering advanced job scheduling functionalities that surpassed those found in its predecessor, MFT.
History
IBM characterized JES1 as "the single most important addition" to the job scheduling capabilities of VS1. The IBM Systems Journal outlined JES1's fundamental services, which encompassed Spooling and scheduling, structured into three primary modules: peripheral services, central services, and queue management.
Although JES1 represented a significant technological advancement, it saw limited adoption. This was largely because users of HASP and ASP systems had heavily customized their setups and were reluctant to abandon their existing investments. Moreover, enhancements to HASP were frequently exchanged informally among users, further discouraging transition to JES1.
Features
JES1 allowed operators to submit batch jobs directly from local unit record equipment. Its Remote Entry Service (RES) facilitated job submissions from distant locations. The subsystem handled output from both local and remote jobs, directing it to local devices, the originating site, or other remote destinations. RES in OS/VS1 functioned similarly to Remote Job Entry (RJE) on OS/360 but employed communication protocols compatible with HASP II and ASP instead of the standard RJE protocol. This early implementation of a client-server architecture utilized BSC and SNA protocols and continues to be operational today.
New Features
- Unlike MFT where reader or writer tasks occupied entire partitions continuously, JES1 required partitions only during task startup or shutdown.
- Whereas MFT stored each SPOOL file as an individual physical sequential dataset on public DASD, JES1 consolidated all SPOOL files within a unified SPOOL dataset.
- In MFT, reader tasks could experience delays caused by interpreting tasks; however, OS/VS1 performs interpretation at the start of the job.
- The JOB Card JCL introduced the TYPRUN=SCAN parameter, enabling rapid submission of jobs for error detection prior to full execution.
- JES1 incorporated a SubSystem Interface (SSI) similar to that implemented in MVS.