| Subject: FAQ:PdoxWin:Net File Rules:2000.01.18 |
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| Written by Mike Irwin | |
| 20 September 2005 | |
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Subject: FAQ:PdoxWin:Net File Rules:2000.01.18 Version 1.0 (2000.01.18) edited by Paradox FAQ Team Reposted by Mike Irwin: 2001.02.10 ==================== 0. Introduction ==================== This FAQ addresses the rules to abide by when setting up a location for a .NET file for Paradox. ------------------------------- 0.1 Legal Info and Disclaimers ------------------------------- Paradox is a trademark of Corel. Borland Database Engine (BDE) is a trademark of Inprise. The information provided in this FAQ is provided "as is" and is not warranted in any way. The information provided in this FAQ is not endorsed or authorized by Corel or Inprise in any shape, form, or manner. The editors claim NO responsibility for ANY illegal activity regarding this file, or as a result of someone reading this file. You may distribute this file, as long as the copies are complete, unaltered, and are in electronic form only. ------------- 0.2 Feedback ------------- Please send feedback in a Corel Paradox newsgroup or the news:comp.databases.Paradox newsgroup to any of the FAQ Team mentioned in the "FAQ: FAQ FAQ" document. Please preface the subject of your post with the string "PDXWIN FAQ" to alert Team members to the function of the message. Please specify the FAQ name and section number the comment applies to, if any. ============================== 1. General Information ============================== Paradox is a client and file based database system. This means that each user has one or more instances of the client (the Paradox program) running on his or her machine. No copies of Paradox need be loaded or running on any central server machine, even if the use of a central data server is part of your design. Each machine running Paradox also loads an instance of the Borland Database Engine, the BDE. This piece of software is responsible for providing the interface between the part of Paradox that you see and the tables and files that store the data. It's for this reason that we concentrate here on what the BDE does and offers, rather than what Paradox offers, which is largely dependent on the BDE. There can only be one instance of the BDE running on a particular machine at any one time. You can have any number of instances of Paradox, for example, running simultaneously, but they will all use the same instance of the BDE. At load time the BDE will read a configuration file. This may be specified by the user if you are running Paradox (see the "-o" command line switch). Amongst other things, this file will define a directory called the "Net Directory". This directory is a common location visible to all instances of the BDE that wish to share Paradox files. In this directory a PDOXUSRS.NET file will exist to record the active instances of the BDE. It is possible to delete this file safely when no instances of the BDE are connected to it. The first time an instance of the BDE loads it will re-create the file if it does not already exist. The BDE offers a number of types of locking for Paradox tables, including "read locking", "write locking", and "exclusive locking" on tables (see the Help topic "Locking Tables"), and the locking of individual records within a table for the purposes of editing. Whenever any such locks are requested a .LCK file is created or updated within the directory that contains the table involved, and reference is made to the .NET file in order to facilitate coordination beteewn instances of the BDE. Note here that it is perfectly possible to have two entirely independent sets of instances of the BDE on one network, each set with its own .NET file. So long as no member of one set is used to access tables in use by a member of the other set, nothing untoward will occur. However, as soon as sharing is required, all the users of a particular Paradox table must also share the same .NET file. ============================== 2. The Rules ============================== The following are, we believe, the minimum necessary and sufficient set of rules to observe in order to achieve an operating set of instances of the BDE on a network where Paradox tables must be shared. 2.1 For each instance of the BDE cooperating on a network there must be a Path Specification to the directory to hold the PdoxUsrs.Net file. 2.2 The path specification shall be composed of a Drive Letter and a Path String 2.3 The Path String must be identical in form (but not necessarily in case) for each and every instance 2.4 The Drive Letter is not restricted in value or case at all 2.5 There are only 4 Rules There are ONLY 4 rules !!!! Forget all about the Paradox.net and Paradox.lck files; they'll have little or nothing to do with you unless you have a system crash. ============================= 3. Recovery ============================== If you are unlucky enough to have a system crash the steps to follow before continuing are: 1. Make all users stop using all copies of Paradox, and remain thus until you have finished. 2. Check all tables for integrity. One recommendation is to have a set of empty copies of all your tables available and a script that exports all the data from your full tables into text files and then puts it back into a set of empty tables again. Remember that, with relational integrity and lookups, the order in which you fill tables does matter ! Most times you will not need this, but on the occasion that you do you will be very grateful for a little planning. 3. Delete all .lck and .net files on all machines with Paradox installed and on all machines where Paradox accesses tables (shared network machines, for example). 4. On every machine check the BDE configuration (if each machine has its own) to ensure that all point to the same Net Directory. 5. Resume operations. 6. Make another backup. 7. Once things are going well again, find out what caused the crash and eliminate the cause. |
