A Guide to uniVerse Hashed Files - Part I
A Guide to uniVerse Hashed Files - Part II
Hashed Files - Internals Structure & Performance
Choosing the Right Parameters
Blocking uniVerse/NT User Logins
Eliminating Overflow
Overflow Due to Large Records
Suggestions on Using CRON
Tip for HP Users
Resize Reports
Access Control Lists vs. File Permissions

A Guide to uniVerse Hashed Files - Part I

The theory of hashing by division is discussed in terms of the uniVerse file parameters. A mathematical example of a hypothetical algorithm is presented to explain how overflow occurs. Because hashing is dependent upon the keys in the file, changing the hashing algorithm causes a redistribution of data in the file.

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A Guide to uniVerse Hashed Files - Part II

The discussion of uniVerse file parameters is continued.

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Hashed Files - Internals Structure & Performance

The Internal structure of uniVerse datafiles is described in terms of the file parameters. The causes of overflow are presented along with a discussion of how hashing works. The impact of overflow on performance described via an experimental study. The statistics from this experiment are included.

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Choosing the Right Parameters

What are file parameters and how do they change the "shape" of the file? The "shape" of a database file is defined by three parameters: type, modulo and separation. To provide a mental picture of a file we will use our favorite analogy of a metal file cabinet with five drawers.

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Blocking uniVerse/NT User Logins

Are there times when you would like a simple way of blocking users from your uniVerse/NT system? It is particularly important to insure that users don't login during maintenance processes such as file resizing.

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Eliminating Overflow

We all know that overflow in files is “bad”—therefore, when we see files with lots of overflow we’d like to get rid of it.  But, where is the overflow coming from and what is it going to take to get rid of it?  More importantly, will the side effects of what we have to do to get rid of the overflow cause us more problems than the overflow?   That’s the issue we want to describe here.

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Overflow Due to Large Records

How much of overflow is due to large records?  If you want an easy way to check a data file, try this quick and easy technique.  We are assuming that you can use the uniVerse line editor or UniData AE editor.

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Suggestions on Using CRON

Are you using cron, the UNIX utility for repetitive background jobs? Many sites use it only for automating their backups. Because file maintenance (as well as system maintenance) is a repetitive job, cron offers a great deal of utility once you "break the code" on how to get it to work.

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Tip for HP Users

We may have told you that some versions of UNIX have the ability to restrict users, other than root, from logging in if a file called /etc/nologin exits. We had seen this functionality on some of our HP client machines but it would not work on ours. Why? We placed a call to HP software support and received the answer.

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Resize Reports

Have you ever wanted to print a report of just those files which you were going to resize?  Here’s a way of printing a report using the list of files from the modified list in the FAST resize screen.

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Access Control Lists vs. File Permissions

When we first converted from Prime INFORMATION to uniVerse on UNIX we struggled with our security plan and finally abandoned an attempt to use UNIX permissions for anything more than a “screen door” kind of protection.  However we had been part of that community of Prime INFORMATION users who used ACLs, Access Control Lists, to provide another solid layer of security at the O/S level.  We wanted this sort of protection from UNIX.  When we first converted to UNIX, ACLs were not available on our O/S.  Now that they are available we have revisited the “why and how” of using them.

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