Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!inkwell!ivan!jhc
From: jhc@ivan.uucp (James H. Coombs)
Newsgroups: comp.databases
Subject: Re: record locking in C-tree on bsd unix
Keywords: bsd unix, C-tree
Message-ID: <54467@inkwell.UUCP>
Date: 25 Jun 91 15:41:24 GMT
References: <1991Jun25.091645.28309@ncst.ernet.in>
Sender: news@inkwell.UUCP
Reply-To: jhc@ivan.UUCP (James H. Coombs)
Organization: IRIS - Brown University
Lines: 24

In article <1991Jun25.091645.28309@ncst.ernet.in> deepak@ncst.ernet.in (Deepak G Patil) writes:
>Does any one know how to lock records in C-tree on bsd unix ?
>
>to my knowledge to lock records C-tree uses system call,
>and bsd unix doesn't support any system call to lock a record in a file,

c-tree invokes lockf().  I find that when we were working on the IBM
RT, I defined lockf() to (0), but I did not have a multi-user
application on that machine.

There are many ways to implement locking:

	1. Write a lock demon that mediates between processes.

	2. Use a multi-threaded server that keeps track of locked
	records.

	3. Put a flag in each record to indicate whether or not it is
	locked.

	4. If simultaneous locking is limited, use flock() and lock
	the entire table.

--Jim