Content deleted Content added
Use z/OS reference for OS, not z/VSE reference; see also; scare quotes; extents |
The formal nomenclature is appendage, not exit |
||
Line 66:
For OS/360 through z/OS, the program provides an 'Input/Output Block'' (IOB) to EXCP; if the program does an EXCP to multiple IOBs, the system processes them in the order that they were requested. For DASD the IOB includes a seek address, ''IOBSEEK'', in the format MBBCCHHR, where M is the extent, BB is the bin for a data cell, CCHH is the cylinder and head, and R is the record number.
==
A comprehensive list of ''[[User exit|exits]]'' (called, in the EXCP context, ''appendages'') allows authorized programs to override or augment many of the system security and data integrity checks. Most of these appendages are supported for compatibility with earlier instances of the OS, but the functions of several have been modified or extended for MVS. The appendages are specified in the DCB as the last two characters of the module name IGG019xx, where xx = WA to Z9, inclusive. These module names are reserved for installation-written appendages. Any other name of the form IGG019xx is reserved for use by IBM access methods.<ref>IGG = I/O Support component prefix; 019 = Open SVC sub-component; xx = sub-function</ref> Appendages must reside in SYS1.SVCLIB (SYS1.LPALIB in SVS or later instances of the OS).
| |||