System Generation (OS)
| Company type | Process |
|---|---|
| Industry | Computer software / Operating systems |
| Founder | IBM |
| Products | Installation and upgrade process for OS/360, OS/VS1, OS/VS2 (SVS), OS/VS2 (MVS) |
System Generation (commonly known as SysGen) is a process conducted in two phases designed for the installation or upgrading of OS/360, OS/VS1, OS/VS2 (SVS), OS/VS2 (MVS), and other related chargeable operating systems. This approach was developed to accommodate customer requirements for defining input/output configurations and selecting system options, particularly since System/360 hardware lacked automatic device identification and installations varied significantly.
SysGen functions through a sequence of jobs executed within the operating system environment. For initial setups, IBM provides a specially prepared driver system that is exclusively intended to facilitate SysGen operations and is not meant for regular production use.
Prior to initiating SysGen, customers must prepare distribution volumes and restore necessary libraries from tape media. These libraries contain essential data, utility programs, macro definitions, and load modules required throughout the process.
In the first stage, assembler macros outlining the system configuration are assembled. Instead of producing object code directly, this stage outputs a job stream for the subsequent phase by utilizing PUNCH pseudo-operations. IBM revised macro definitions in conjunction with changes to OS/360 option terminology—for instance, terms such as SSS, MSS, and MPS were replaced by PCP, MFT, and MVT respectively by Release 13. The later introduced M65MP represents a variation of the MVT type.
Key system elements are defined within the Stage 1 macros: the CTRLPROG macro identifies the control program variant; while the SCHEDULER macro designates the scheduling method, which evolved from simple values like SEQUENTIAL and PRIORITY to more complex types aligned with control program categories.
The recognized control program variants include:
- PCP
- Primary Control Program (Option 1)
- MFT
- Multiprogramming with Fixed number of Tasks (Option 2)
- MVT
- Multiprogramming with Variable number of Tasks (Option 4)
- M65MP
- Model 65 Multi-Processing, a specialized form of MVT
The GENERATE macro triggers a complete generation of the operating system, including compiler and library builds or updates to I/O configurations. For MVT installations incorporating TSO, an equivalent function is performed by the TSOGEN macro.
During Stage 2, the previously generated job stream is processed using utilities such as the assembler and linkage editor to complete system generation.
Although SysGen was once an essential procedure, it has been replaced by more advanced tools including SMP/E, IOCP, MVSCP, and eventually Hardware Configuration Definition (HCD), reflecting IBM's progression in system management methodologies within their operating environments.
See also
External links
- IBM, Input/Output Configuration Program User's Guide and ESCON Channel-to-Channel Reference
- IBM, z/OS V1R1.0 HCD Planning