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Old Tools and New Applications:

PKZIP for the AS/400

(a product review, and then some…)

By Thibault Dambrine

It is difficult to write a product review for something you like without making it sound like a plug, but I will do my best to make this a learning experience (as opposed to simply exposing my one-sided opinions). Notice, in my defense, that it’s a nice change to read about something different than IBM’s latest accomplishments! (No slur intended here, I actually like IBM. This company contributes significantly to my livelihood!).

The article will be presented in the TUG Magazine in two parts: Part 1 (This issue): An introduction to PKZIP for the AS/400, how we came to use it in a concrete situation and a list of pros & cons. Part 2 (Next Issue): A brief look at Data compression. Several data compression algorithms will be covered how they work, and how they are used by PKZIP.

Part 1: PKZIP, the Product

For those who have not read my recent articles, I have done a fair bit of work lately in the area of FTP and FTP programming on the AS/400 (see the TUG web site). Using File Transfer Protocol naturally leads to transferring data, (sometimes large quantities of data).

A few weeks ago, one of my colleagues who is in the same realm asked me if FTP had any ability to compress data before sending it, or if there was any way to speed up an FTP transmission. My first answer to this was no. There is no data compression feature on FTP. It simply transmits byte by byte. Short of creating a sub-system simply to handle the transfers, there is not much to do for speeding up an FTP transfer with the tools supplied with the OS/400 Operating System. As a second thought, I told him something else. A few years ago, while I was handling the advertising for the TUG Magazine, a company that manufactured an AS/400 version of PKZIP approached me for prices. The ad deal did not materialize but I thought it was an interesting concept.

Armed with this information, we found what we were looking for on the World Wide Web: a company named ASCENT SOLUTIONS Inc. or ASi. One of ASi’s products – PKZIP for the AS/400 – is the subject of this article.

We tried the product on large physical files (more than 1 million records) and achieved surprisingly good compression ratios. The files we used were compressed to between 5 and 20% of their original size. The actual "zipping" time took on average about 5 minutes in daytime processing for these files. Every byte was restored properly when we unzipped the file on a different platform. Even with the compressing and decompressing time, we made some significant savings in the overall duration of the process when sending data using FTP. As you can imagine, these results will vary with the type/quantity of data and the processor used.

Another application we found for this most effective tool could be for archiving purposes. The ability to use a small fraction of the media necessary to store large files that are seldom used can be very appealing. Here is a summary of the characteristics we liked and the ones we did not like:

The Pros:

PKZIP for the AS/400 has (amongst others) the following characteristics that I like:


The Cons:

On the other hand, here are the points that make PKZIP for the AS/400 a utility not suitable for all applications:

There is one important factor one should also be aware of: with PKZIP for the AS/400, we are out of the shareware territory. PKZIP for the AS/400 is not free. This is the price list I obtained from ASi. The product is tier-priced, as are so many other software packages available on the AS/400.

Here is the price structure for this product, as of September 98:













There are volume discounts available:

# of Machines

% discount










Call for quote


In a Nutshell

Overall, I found PKZIP for AS/400 presents itself well. Its best advantage is the portability of the compressed files it produces. However, when purchasing this utility, one has to be aware of its limitations, especially as an AS/400 only utility. By itself, it is not a tool for every compression situation. If you want to compress source files, or other AS/400 files that require keeping the DDS structure, you have to save them in a *SAVF type file before Zipping it up. This may be more effort than it is worth (remember, this utility costs money now). For transmitting large amounts of streamed data, as we have done in the project that spurred us into looking for compression solutions, it worked out great. I found PKZIP did what it claimed it could do, and did not give us any surprises.

This article will be continued in the next issue, with a presentation of Compression Algorithms & Technical Highlights.

Credits, Disclaimers and Other Definitions:

ASCENT SOLUTIONS Inc. can be found on the World Wide Web at, where I have also found valuable information used in this article. Other articles on FTP and other AS/400 related subjects can be found at , the TUG web site. The author has no links or partnerships of any kind with ASCENT SOLUTIONS Inc. The author thanks the individuals who took time to proofread this paper before it went to press. T<G

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