Hierarchical File System (IBM MVS)
{{about|HFS in MVS|HFS in MacOS|Apple HFS|other|HFS (disambiguation)}}
{{Infobox Filesystem
| full_name = z/OS Hierarchical File System
| name = HFS
| developer = IBM
| introduction_os = DFSMS/MVS Version 1.2 for MVS/ESA
| introduction_date = 1993
| partition_id =
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| compression =
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| OS = included in z/OS (until 2.5), all releases of OS/390, and MVS/ESA V5R1 and higher (optional for V4R3)
}}
IBM's Hierarchical File System (HFS) is a POSIX-style hierarchical file system{{Cite book |last=Hoskins |first=Jim |url=https://books.google.com/books?id=NtHhpIjIFMEC&pg=PA231 |title=Exploring IBM EServer ZSeries and S/390 Servers: See Why IBM's Redesigned Mainframe Computer Family Has Become More Popular Than Ever! |last2=Frank |first2=Bob |date=2003 |publisher=Maximum Press |isbn=978-1-885068-91-0 |language=en}} for the MVS/ESA/SP through z/OS operating systems.
IBM introduced HFS on February 9, 1993 in MVS/ESA System Product Version 4 Release 3 OpenEdition{{cite web
| title = OPENEDITION SERVICES ON MVS/ESA SP VERSION 4 RELEASE 3 ANNOUNCED AND AVAILABILITY OF MVS/ESA SP VERSION 4 RELEASE 3 WITH ADDITIONAL ENHANCEMENTS
| id = 293-060
| date = February 9, 1993
| url = https://www.ibm.com/common/ssi/ShowDoc.wss?docURL=/common/ssi/rep_ca/0/897/ENUS293-060/index.html
| access-date = January 28, 2022
| publisher = IBM
| work = Announcement letters
}}
{{cite web | url=http://www.redbooks.ibm.com/redbooks/pdfs/sg245482.pdf | title=Hierarchical File System Usage Guide | accessdate=2016-09-01 | date=September 2000 | publisher=IBM }} with DFSMS/MVS Version 1 Release 2{{cite web
| title = DFSMS/MVS Version 1 Release 2
| id = 294-095
| date = March 1, 1994
| url = https://www.ibm.com/common/ssi/ShowDoc.wss?docURL=/common/ssi/rep_ca/5/897/ENUS294-095/index.html
| access-date = January 28, 2022
| publisher = IBM
| work = Announcement letters
}}
for 3090 mainframes. On April 6, 1994, IBM introduced MVS/ESA System Product (MVS/ESA SP) Version 5 Release 1,{{cite web
| title = IBM MVS/ESA SP Version 5 Release 1 and OpenEdition Enhancements
| id = 294-152
| date = April 6, 1994
| url = https://www.ibm.com/common/ssi/ShowDoc.wss?docURL=/common/ssi/rep_ca/2/897/ENUS294-152/index.html
| access-date = January 28, 2022
| publisher = IBM
| work = Announcement letters
}}
which included MVS OpenEdition (MVS-OE) with HFS as a standard component. IBM continued providing HFS through z/OS 2.4 for z System mainframes.
IBM functionally stabilized HFS starting with z/OS 1.7, in 2005.{{cite web |last1=Shacklett |first1=Mary E. |last2=Bigelow |first2=Stephen J. |title=What is z/OS? |url=https://www.techtarget.com/searchdatacenter/definition/z-OS |website=TechTarget |access-date=March 2, 2023}} The z/OS File System (zFS) was released as the higher performance successor to HFS in 1995, and IBM recommended migration from HFS to zFS. Following the release of zFS, z/OS releases included a tool, BPXWH2Z, to convert HFS to zFS.{{cite web | url=http://www.redbooks.ibm.com/redpapers/pdfs/redp4328.pdf | title=HFS to zFS Migration Tool | accessdate=2016-09-01 | date=January 2008 | author=IBM }}