nick@aimed.UUCP (Nick Pemberton) (08/18/89)
[I tried this via email; didn't work (bounced) soo now y'all get to read it... ] > Does anybody out there in the land of data bases know anything about > the Pick operating system and its data base structure? > I could tell you a great deal about PICK - we operate several pick machines, and we have a resident prime expert (ross@aimed.UUCP) True Pick is essentially an operating system built around a database. Everything in pick revolves around files (which are vaguely similair to directories). Files store within them *items*, which are the equivalent of files on unix. The difference is that the files store items in them using scatter-storage, or hashing. One must specify the modulo, or number of buckets, in a file based on how much is likely to go in a file. Files may have pointers to files within them, and this is is how the system is built: The Os knows of one file, SYSTEM, which is like the root directory under unix. All accounts are files pointed to within SYSTEM, and all accounts then have their own structure beyond that. There is no limit to how many items may be in a file, since if a bucket overflows, another frame (block) is linked to the bucket. System performance degrades if buckets are allowed to overflow much, because there is only one hash done, and then the search is linear within a bucket. Rebuilding files is trivial, and part of the OS. > We have recently got an HP9000 835S series. It runs Pick on top of > HP's Unix (called HP-UX). We needed pick to be able to run the > application program we bought, which was originally written for Pick > in Prime computers. > Be interested to know what that is... > I am not very much interested in interaction between Unix and Pick, > but more interested to learn about Pick system and any insight to > its multivalue field capabilities in its data bases. Multivalues are actually nothing special - Items, those units that appear in files, are actually just one big string. They are divided into Attributes, then into Values, then into subvalues. This actually works using delimeters. The OS has a large number of utilities built into for manipulating the string, placing things between AMs VMs and SVMs. The only data type on the system is the string. This does carry some overhead, and makes PICK useless for number crunching, which it was never intended to be used for. Feel free to contact me if you need to know more. -- Nick Pemberton uucp: !{lsuc, uunet!mnetor}!aimed!nick AIM, Inc bus: (416) 429-1085 Toronto, Ontario, Canada Home: (416) 690-0647