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→File system structure: reference the z/VM page for this control block, which doesn't seem to have changed much. |
→File system structure: EDF in VM/SE R2 and VM/BSE R2 |
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Records are usually called ''items'' in CMS terminology. CMS files can have either ''fixed'' or ''variable'' record format; record types may not be mixed in a file. For fixed-length records the length is defined by FSTLRECL, and the ___location of any fixed-length record can be computed by (item_number-1) * record_length/800. The quotient will be the block number and the remainder will be the offset of the item in the block. Variable-length records have a maximum length of FSTLRECL bytes, and are preceded by a two-byte record length field indicating the actual length.
In 1979, Virtual Machine/System Extensions (VM/SE or SEPP) Release 2 and Virtual Machine/Basic System Extensions (VM/BSE or BSEPP) Release 2 provided an enhancement<ref>{{cite conference
An enhancement to the original CMS file system in [[VM/SP]], called ''Enhanced Disk Format'' (EDF), allows larger files by expanding the FST and introducing multiple levels of chain link blocks.<ref>{{cite web|title=The CMS EDF file system|url=http://dforeman.cs.binghamton.edu/~foreman./550pages/VM/CMS-File-System-1.doc|website=binghamton.edu|accessdate=August 5, 2016}}</ref><ref>{{cite web|last1=IBM Corporation|title=FSTD|url=http://www.vm.ibm.com/pubs/cms530/FSTD.HTML|website=ibm.com|accessdate=August 5, 2016}}</ref>▼
| conference = SHARE 89
| title = VM and the VM Community: Past, Present, and Future
| at = Sessions 9059-9061, M. After the Doubtful Decade
| quote = 1979 brought us VM/370 Release 6 and Release 2 of BSEPP and SEPP, with logical device support, the EDF file system,
| author = Melinda Varian
| date = August 1977
| url = http://www.leeandmelindavarian.com/Melinda/25paper.pdf
}}
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==See also==
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