In TSS/360, VPAM datasets can have both sequential and index sequential 
members; you can read and write withing a member either sequentially or by key, 
including inserting a new record between existing members. VIPAM is a 
colloquial term for a VPAM dataset containing VIS members. From the 
documentation:

     Three special Data Management Access methods -- the virtual Access
     Methods (VAM)-- have been provided with TSS. They are specifically
     designed for a time-sharing environment and are used to read and write
     data to and from direct access storage devices. For all three of the
     VAM access methods, the data set management (for example, formatting)
     is performed in virtual storage -- using virtual addresses that are
     part of the user's virtual storage address space -- although physical
     device management (e.g., I/O) is performed by system programs in
     resident storage.  Each access method provides access and processing
     capabilities for data sets organized in a specific manner.

          * sequentially (Virtual Sequential Access Method -- VSAM)

          * indexed sequential (Virtual Indexed Sequential Access Method --
            VISAM)

          * partitioned (Virtual Partitioned Access Method -- VPAM)

     In TSS, data sets organized for processing by one of the virtual
     access Methods are generally referred to as VAM data sets.

and

     Partitioned Organization
          A data set with partitioned organization has elements, or
          members, that are other data sets; these elements are in either
          sequential or indexed organization.



--
Shmuel (Seymour J.) Metz
http://mason.gmu.edu/~smetz3

________________________________________
From: IBM Mainframe Discussion List [IBM-MAIN@LISTSERV.UA.EDU] on behalf of 
Clark Morris [cfmt...@uniserve.com]
Sent: Monday, June 29, 2020 11:15 PM
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: Re: Virtual SHARE Ageenda

[Default] On 29 Jun 2020 18:05:01 -0700, in bit.listserv.ibm-main
sme...@gmu.edu (Seymour J Metz) wrote:

>Re FBA, they did it for other systems, and TSS/360 used page formatted volumes 
>for everything except compatibility volumes, so from a technical perspective 
>it's a no brainer, although direct use of SCSI DASD might make more sense 
>these days. Politically, it's a thorny issue. I'd love to see them extend VSAM 
>to the level of TSS while they're at it, e.g., VIPAM.

What is the logical difference between VPAM (found it in a TSS360
description) and PDSE except PDSE is an add-on (my opinion of the
decision maker who decreed that PDSE or at least a read-only subset
didn't need to be available for SYS1.PARMLIB, SYS1.NUCLEUS and
SYS1.LPALIB is complete contempt)?

Clark Morris

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