On 5 November 2010 08:42, John Eells <ee...@us.ibm.com> wrote:
> Originally, TSO/E user IDs were kept in the User Attribute Data Set (UADS),
> a PDS. User IDs with few attributes fit in a single member. User IDs with
> many attributes overflow into multiple members. The member naming
> convention is USERIDn, where n is a digit from 0 (the first member) to 9.
> You can control when IDs overflow by changing the block size; smaller block
> sizes split sooner, and larger ones split later.
>
> TSO/E looks at all the USERIDn members when you log on to retrieve all your
> user attributes.
>
> This architecture (created when memory and storage were still very
> expensive!) causes the eighth character in the member name to be reserved
> and leads to the 7-character user ID restriction that persists today even if
> you use your security database for use attributes rather than UADS.
The exact order of events in the design and implementation of TSO is
not entirely clear, except perhaps to someone who worked for IBM
around 1969 and has a good memory. There were related products that
also implemented 7-character "userid"s, or userid-like things, and I
suspect some of the code was shared. Notably, OS/VS1 had an RJE
facility run by its JES (not to be confused with JES2 or JES3 on MVS),
and it had the notion of a remote "station" which had a 7-character
name. It also had a UADS-like dataset in which it stored the relevant
configuration data. Some of this became comingled with TSO, with the
result that in the early days the DEST keyword of TSO's ALLOCATE
command supported only 7-character destination names, even though JES2
and JCL allocation supported 8. This was corrected only very late in
the game - 1980s, I think. You can see in the code from the MVS 3.8
base ALLOCATE command, where not only is the DEST length restricted to
7, but it is referred to as a remote user:
* USERIDS FOR THE DEST KEYWORD Y02676 01994000
USERID IKJSUBF 01995000
USER IKJIDENT 'USERID IN THE DEST SUBFIELD', X01996000
MAXLNTH=7, X01997000
FIRST=ALPHA, X01998000
OTHER=ALPHANUM, X01999000
PROMPT='USERID FOR THE DEST SUBFIELD', X02000000
HELP='LOGON ID OF A REMOTE USER' 02001000
Tony H.
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