More locking stuff: I knew about READU (sic) since late 1978 when I worked at microdata. I also knew that it worked on the group level and not the record level.
That wasn't particularily problematic as even consecutive records occupy different groups and there wasn't any conflicts. Verbs like List-Locks (sic) used to illustrate the offending frame and now they illustrate the item and the owner of the readu lock. The LOCK/UNLOCK command is often mis-understood. It is a system level locking mechanism used to prevent conflicting application processes, like entering vouchers when running checks or entering orders when processing invoices. Basically, I have never found them used in this fashion as most programmers use a CONTROL file with status's. All of those that have LOCK/UNLOCK usually use them around read/write which I deem overkill. Now that most systems have FILELOCK that would replace the LOCK/UNLOCK wrapper for read/write. Actually it's better than LOCK/UNLOCK as it takes two to tango and even if you had: LOCK 1 ELSE blah, blah SELECT FILE LOOP WHILE READNEXT ID DO ; PROCESS ; REPEAT UNLOCK 1 You would have to have any conflicting processes participate with the LOCK. In the example above, the FILE is not protected by anything unless that second process also has LOCK 1 ELSE. Having READ REC FROM FILE THEN WRITE REC blah would successfully breeze past the LOCK/UNLOCK scenario from above. Thanks for everyone's input. ----- Original Message ----- From: "Eugene Perry" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Monday, July 05, 2004 11:05 AM Subject: Re: [U2] READU vs LOCK > In the early days, it was group locking rather than record locking. > However, this technique locks the entire file. > > Eugene > > ----- Original Message ----- > From: "Martin Phillips" <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Sent: Monday, July 05, 2004 7:39 AM > Subject: Re: [U2] READU vs LOCK > > > > Mark, > > > > I may be wrong, but I have a vague memory that in the very early days, > > multivalue databases (Pick?) didn't have record level locking. > > > > Use of LOCK/UNLOCK is hard to justify and probably even harder to get to > > work without endless deadlocks. I came across a legacy application > recently > > that had no locking at all! > > > > Martin Phillips > > Ladybridge Systems > > 17b Coldstream Lane, Hardingstone, Northampton NN4 6DB > > +44-(0)1604-709200 > > ------- > > u2-users mailing list > > [EMAIL PROTECTED] > > To unsubscribe please visit http://listserver.u2ug.org/ > ------- > u2-users mailing list > [EMAIL PROTECTED] > To unsubscribe please visit http://listserver.u2ug.org/ ------- u2-users mailing list [EMAIL PROTECTED] To unsubscribe please visit http://listserver.u2ug.org/
