Will You can visualize the lock table as consisting of a number of columns and rows. The size of these are dictated by your uvconfig settings.
The group lock table has GSEMNUM rows, each with GLTABSZ entries. The readu lock table has GSEMNUM rows, each with RLTABSZ entries. The group lock and readu lock tables are both linked through the GSEMNUM. To protect access to these whilst giving a reasonable spread of locks, each row of the table is protected by a specific semaphore. When Universe needs to take a group lock, it calculates the row that should hold that lock in a similar way to how it goes about calculating the right block to store a record in a hashed file: it converts the lock into an address (group address + inode), divides it by GSEMNUM and the modulus gives the row in which to try to place the lock. It means that like a hash file you can have concurrent access to different parts of the lock table. Brian -----Original Message----- From: u2-users-boun...@listserver.u2ug.org [mailto:u2-users-boun...@listserver.u2ug.org] On Behalf Of Wjhonson Sent: 06 November 2012 17:59 To: u2-users@listserver.u2ug.org Subject: Re: [U2] Is the LMODE column helpful for something? Okay it's called a "lock semaphore" What is that, and why would two different users have the same lock semaphore? -----Original Message----- From: Wjhonson <wjhon...@aol.com> To: u2-users <u2-users@listserver.u2ug.org> Sent: Tue, Nov 6, 2012 9:37 am Subject: [U2] Is the LMODE column helpful for something? In my lock table there is a column called Lmode it has a two digit number and also "RU" which I guess means "Read Update" although I haven't tested other types of locking. What is this two-digit number and can it be useful to me for something? It's not unique across users, and also one user can have several simultaneous values. What is it? _______________________________________________ U2-Users mailing list U2-Users@listserver.u2ug.org http://listserver.u2ug.org/mailman/listinfo/u2-users _______________________________________________ U2-Users mailing list U2-Users@listserver.u2ug.org http://listserver.u2ug.org/mailman/listinfo/u2-users _______________________________________________ U2-Users mailing list U2-Users@listserver.u2ug.org http://listserver.u2ug.org/mailman/listinfo/u2-users
