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client server question

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    client server question

    People on this board have mentioned that a "client server" version (v6) of A5 is in development. And some of my more tech-savy colleagues have told me that A5 is basically a toy because it is a "file server" not "client server" database. (Although we have developed things in A5 that the priesthood failed to acomplish in Oracle.) I am really displaying my level of ignorance here, but could someone explain in simple terms what makes a client server database different from A5. Thanks in advance for any education.

    -Bill

    #2
    RE: client server question

    Bill - this is probably a gross over-simplification, but put very simply (the only way I know how) -

    In a "fileserver" system, each user actually has access to the file data, and may update it - "locks" prevent multiple up-dates, you have to wait your turn if a record is busy. It operates pretty much the same way as a single user system, except the actual data is on a "server", and all users are sharing the file in real time.

    In a "client server", you (the user) are actually making a request to the server to view/modify data. "It" does an SQL and returns a copy of the data to you. Same with your requests to modify - you modify the data on your computer, and send a request back to the client server to change the "real" data. Your data is put into a que, and the file is updated in time sequence.

    In a system with relatively few users or small amounts of date, a file server is perfectly acceptable.

    At least this is my understanding.
    For REALLY good information, goto www.landfield.comfaqs

    Lowell

    Comment


      #3
      RE: client server question

      Sorry - that should be www.landfield.com(backslash)faqs

      Lowell

      Comment


        #4
        RE: client server question

        Thanks Lowell, that's a great explaination. I'll take a look at the site you recommend too.

        -Bill

        Comment


          #5
          RE: client server question

          Hi William,

          >>some of my more tech-savy colleagues have told me that A5 is basically a toy because it is a "file server" not "client server" database

          Comment


            #6
            RE: client server question

            Good analogy Jim. I must admit though, the pile in the back of our pickup is getting pretty high. -Bill

            Comment


              #7
              RE: client server question

              The explanation of client serever architecture above was very good, and the faq that was recommended was very informative. One more question though - when you create an sql table in a5 (i.e. connect to a client server odbc data source like oracle), are you achieving the network load benefit of client server architecture - i.e. are query definitions processed on the server and result sets (only) sent back? Thanks for any input.

              -Bill

              Comment


                #8
                RE: client server question

                Hi William,

                >>are query definitions processed on the server and result sets (only) sent back?

                Comment


                  #9
                  RE: client server question

                  I read some of the info on three-tier architecture at the faq site you recommend above, but I was not clear on the advantage of three-tier. Wouldn't locating business rules in the client (gui) maximize load distribution and minizize unnecessary network traffic by making those evaluations/edits/transformations locally, instead of at a centralized middle tier? -Bill

                  Comment


                    #10
                    RE: client server question

                    Bill, I suspect the answer to your question is yes, but...

                    Consider the maintenance issues. When a business rule changes each workstation must be updated if they're stored locally. A middle layer might make it much easier to implement a system wide change.

                    -- tom

                    Comment


                      #11
                      RE: client server question

                      Tom: I was thinking that this might be the reason. On the other hand though, changes in the client/gui happen, and any sizable system would probably have an automated mechanism for intregating those changes into the local installations (i.e. an automated shadow_refresh() routine). There must be some other logical reason for the middle tier, but I'm just not seeing it. - Bill

                      Comment


                        #12
                        RE: client server question

                        Hi William,
                        >>, changes in the client/gui happen, and any sizable system would probably have an automated mechanism for intregating those changes into the local installations

                        Comment


                          #13
                          RE: client server question

                          Jim: - Isn't the web (or a large system on a corporate intra-net using a browser-based interface) the ultimate example of a situation where the client/gui is refreshed each time the user logs on? In that case, isn't the client/gui tier of the interface completely contained in the web pages that the user interacts with? Therefore any business rule/field rule changes that were incorporated into a web page would be present and processed on the user's machine each time he/she opened the changed page. In other words, wouldn't a browser-based interface take care of (standardize) the problem of not knowing the particulars (os, etc.) of the machines that might log on? -Bill

                          Comment


                            #14
                            RE: client server question

                            Hi William,

                            Yes, but you are making my case for me. When you log on with your browser you may be interacting with only a simple web server, but you may be interacting with several layers of servers (ie: middle tier) Your request may be validated by the middle tier before your request is allowed to access the data or write to the data etc. etc. The end user's system doesn't need to know anything about this. For instance, lets say you were filling in an on line form. The middle tier (business rules) could be called first to check that you filled in the zip code before passing the request to the database server. The thought is to segment and compartmentalize the process for ease of maintinance, portability, troubleshooting etc. Really not that much difference than a lot of good Alpha practices. We don't hard code paths, we break our data down into smallest descrete data, we create portable code whenever possible, use functions rather than rewriting code, etc.

                            Jim

                            Comment


                              #15
                              RE: client server question

                              Jim: Thanks for all the responses. I don't mean to drag this topic out, I'm just finding the discussion interesting. So, one more question. In the hypothetical case you propose above, wouldn't it be more efficient to check whether the user filled in the zip code field correctly with the java code (or html, or whatever - I am a novice) which is running in the user's browser before data is even sent back to the host web server? Wouldn't this maximize processing distribution and minimize unnecessary traffic, leaving the web server free to devote all its resources to legitimate requests?

                              Any changes made to these checks (business rules) would be made in the web pages' code, and therefore would be "shadow.refreshed()" each time the user requested the changed web page (i.e. they would get the changed/updated page).

                              Limitations in what can be done with java/html etc. may be the reason for not doing this. As I mentioned, I am a novice and I am still just experimenting with querying my A5 tables and displaying the results in a web page - I have not gotten to the point of updating them from a browser yet. Maybe the amount of edit/transformation code that you can locate in a web page is severly limited.

                              Thanks for all the back and forth on this. This board usually focuses on more practical problems - which is good. But I think this will have practical applications for me, and possibly others here. And beyond that, it's kinda interesting. -Bill

                              Comment

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