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Network Slow

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    Network Slow

    My problem is that my network performance is slowing down when we are adding records to my tables. When I initially set-up the network 6 weeks ago the Alpha performance was electric. No other utility programs are running on any machines. Can anybody give some advice?


    My network consists of 5 Pentium machines lowest spec 300 CPU and 64 Meg ram using Windows 98 second edition using Alpha 5v4.3 database files (only) networked

    Using files from a HP E60 Netserver with Pent500 and 256mem using Windows NT Server 4 operating system.

    #2
    RE: Network Slow

    Indexing could be a slowdown source for record entry. As you add records, Alpha must keep the indexes updated.

    How many indexes do you have defined for the table accepting data entry, and how complex are they? Any full text search indexes?
    There can be only one.

    Comment


      #3
      RE: Network Slow

      Stan,

      Adding indexes does NOT slow down Alpha significantly unless

      1. You are saving records (either adding or changing) faster than every 1 or 2 seconds
      2. You have a lot of indexes that need to be updated upon the save (like 100's of a set that has a lot of children where editing of children is possible)

      Assuming no changes were made to the application, adding records can cause queries and filters to be slower if you don't create queries that allow LQO (Lightning Query Optimization), but this is only during the query part that it get's proportionally slower. Since only one index is active for any one window of the data, the number of indexes and the number of records is irrelavant. To prove this to yourself, try doing a find (not a query) on a current index using 10 records, or 10 million records, whether there is 1 index or 24 indexes. It will be almost the same.

      The most likely case is that a Network Card or Network cable is bad (generally the connectors). This can cause numerous network retries and slow the whole network down. Disconnect each station at the network hub and see if it speeds up to try to isolate this problem.

      It's also possible that a workstation is running slower due to lack of RAM or virtual disk space. This would affect Alpha if that station were running the application.

      Regards,

      Ira J. Perlow
      Computer Systems Design & Associates
      [email protected]
      Regards,

      Ira J. Perlow
      Computer Systems Design


      CSDA A5 Products
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        #4
        RE: Network Slow

        Ira,

        Appreciate the response and information. With no more information given than was present, I was only suggesting

        "Indexing could be a slowdown source"

        a possible starting point.

        Have a good weekend.

        Stan
        There can be only one.

        Comment


          #5
          RE: Network Slow

          Ira, I would like to think I am wrong and you are right, but as few as 6 people doing data entry on the same large table with 10 indexes most certainly can cause problems (slow downs and can't add key to tag errors, records locked that are not locked, etc.) that are clearly related to the indexes (i.e., removing the indexes removes the problems). Indexes on date fields seem to be the main culprit. I have been unable to get a fix for this because unless Selwyn gets 6 people to sit down and bang away for a while the problems never show up. And I am not the only one who has nad similar problems. A large primary table (500,000+ records) may also be part of the mix that produces the problems. I have reluctantly come to the conclusion that this is just one thing that A5 is not well suited to do.

          Ray

          Comment


            #6
            RE: Network Slow

            Raymond:

            I agree with Ira on this one. We have found that
            indexes do not really slow the system down per se.
            Now, Filtered indexes can and do cause heap lock problems.

            We found that most of our unable to add key to tag problems
            resulted from a too slow network, a too slow server and
            a hub instead of a switch. Once we upgraded to 100 mhz,
            to a 100 switch instead of a hub, and to a very fast server
            with lots and lots of ram and lots of free fast harddrive space, we were only left with heap lock failures which by removing as many filtered indexes that we could have even reduced our twice a day heap failure.

            Now, we rebuild our indexes each night and after any major
            crash. We do not use queries however, because so far
            we have not found them to be quick enough for production.
            I have been following IRA's posts regarding his lighting
            queries and since I have found him on target for many years
            we are looking into how to utilize his method for our
            system.

            I believe that we would qualify as a system as complex and
            scaled as yours with many more indexes, tables and operations.

            What is your network, what speed, server and cards, do you
            have a switch, what OS?





            Comment


              #7
              RE: Network Slow

              2 cent time. (Did I hear a groan out there?)

              I would have to agree with Ira. Our app has about 14 databases and about 45 tables with large indexes, and over 360 layouts, @ 125 saved operations, and @ 55 global scripts (many running over 300 physical lines of code). Our primary database has been cut to 16 tables (2 @ 365 K records each, 2 others adding to 365 K, 2 @ 470 K each, one around 85 K, a few in the 50 K range, the rest under 5 K records). As has been indicated in previous posts, we are notorious for having what some consider to be an excessive number of indexes (including many with boolean filters). Our primary table had around 25 to 30 indexes. Depending on what specific task is being performed (such as development testing or troubleshooting), I myself have had 3 or more databases and individual table browses open on a Win 98 network station based on a 300 with 128 M RAM. This is with editing going on in more than 1 table (and more tahn 1 instance of a table), easily representing 3,000 K to 5,000 K records. No appreciable speed degradation. But the system has over 5 G of available drive space for swap files, etc, and has defrag run on it at least every month or so. (Home system based on a 600EB with over 35 G available on the 7200 RPM boot drive is actually faster than the 750 with a 12 G hard drive in the office which has more RAM.)

              Our progression of servers over the last year or so has been a 300, 550, and now a 750. At each upgrade we moved the replaced systems to the floor and bought a couple more, thereby upgrading all systems. Most systems are now 500 or 550's with 128 M RAM MINIMUM (256 on most). Each system has at least a 10 G hard drive.

              This progression has resulted in a network with almost no time lags for creating / updating records in a high-volume transaction processing operation. Each transaction can have up to about 2000 FIELDS of info associated with it. Almost every operation creating/editing/processing a transaction uses a fair number (at least 50 to 10) field rule based lookups and/or script based. Every operation does at least 2 lookups to create/edit non-attached tables.

              As everyone on the networks gets a faster more efficient system it also seems to speed up the network.

              Comment


                #8
                RE: Network Slow

                Concerning the speed of the client (workstation) computers.

                The basic speed of the client is not really relevant to the speed of the system overall, EXCEPT

                That every time a record is accessed (or a group of records), a set of file lockings and unlockings, as well as record locking and unlockings must occur on the network. In a true client-server database, this is performed by the server.
                HOWEVER, Alpha 5 is not a true client-server program (currently anyway). (Neither is Access, FileMaker Pro and others too). This means that the client stations must perform this sequence of operations (at which time all other clients must wait). If the client is slow in doing this for any reason, it slows the whole system down. Multiply this by many clients accessing many records and it can add up to performance degradation.

                Thus, the speed of the Network, the quality (and latency) of the the Network Interface Card (NIC), the numbers of errors on the network all have some affect. A secondary issue is the speed of the client workstation, which adds a small (but not necessarily insignificant) contributing factor. Thus, clients that are way too slow (today that means
                Regards,

                Ira J. Perlow
                Computer Systems Design


                CSDA A5 Products
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                Comment


                  #9
                  RE: Network Slow

                  The network I was referring to is not the fastest around but it is also not especially slow. I don't have the specs in my memory banks right now, but it is a farily recent Compaq NT server with what normally would be sufficient RAM, a very nice HP hub and all NICs are 3Com and all cabling is high quality. The workstations are a tad on the slow side (don't know specs right now).

                  BUT, this setup runs other non client server database without such hitches. If I have to tell my client that to use Alpha Five he'll have to drastically upgrade his hardware along the lines some of you are suggesting, he'll boot my butt (and Alpha Five) right out the door. Some of you clearly have hardware budgets that most of my clients can only dream about.

                  AND THE FACT REMAINS, if I remove just the date indexes, almost all of the problems go away. The problem is that doing away with those indexes weakens the app in other areas.

                  Ray Lyons

                  Comment


                    #10
                    RE: Network Slow

                    What do your SETS look like and what are the linking fields?

                    If you have not created a well designed set, that can cause some problems and will be compounded if your linking fields are expressions.

                    Addtionally, the problem will be compounded even further if you have not properly coded for a multiuser envirionment which can result in index corruption and the infamous "tag error".

                    I suggest you review your sets (if any) and determine if they are properly linked and indexed. Also, review your multiuser envirionment and verify that it is safe and accurate. That means get down with paper and pencil (the old fashioned way) and prove it is correct. You'd be surprised how many people I tell them to prove their multiuser envirionment on paper who can't do it and find the reason for their error.

                    Comment


                      #11
                      RE: Network Slow

                      I'd have to disagree. The "can't add key to tag errors" are more like to be related to incorrect multiuser handling on the part of the application programmer.

                      I used to think this was an index problem too, but I discovered that the index corruption was only a symptom. The real culprit is multiuser handling.

                      Sincerely,
                      Jose

                      Comment


                        #12
                        RE: Network Slow

                        Jose, I'd be interested if you would good enough to outline what you mean by 'proving' a design is safe and accurate for multi-users. This is an area that I would like to improve in my own work.

                        -- tom

                        Comment


                          #13
                          RE: Network Slow

                          Multiuser programming is several courses in themselves. But I can get you started with a book reference. This book contains proofs and theorums for all the major concurrent algorithms and shows you how to proove a system.

                          It is an old book called "Principles of Concurrent Programming". This got me through university. It discusses the principles and thus can be applied to any system. I've been in programming for so long that I use the principles intuitively when designing A5 applications so it is more difficult for me to explain than when I was in university.

                          If you are interested to help yourself, the ISBN for the book is 0-13-701078-8. Author is M. Ben-Ari at Tel-Aviv University. Publisher Prentice-Hall International.

                          Jose

                          Comment


                            #14
                            RE: Network Slow

                            Thanks, I'll check it out.

                            If you were to write up an article outlining the key points, tips or pointers you regularly employ, I'm sure this would be of great assistance to many.

                            Thanks.

                            -- tom

                            Comment


                              #15
                              RE: Network Slow

                              Ray,

                              Based on what I'm saying and others, I think you should be convinced that Alpha 5 should not necessarily be slow. And assuming the network is in good condition, then you need to ascertain the difference in A5 technique used and change the method. This could mean an A5 bug or just a general limitation.

                              Are you using an index based solely on a date field? (you can tell, because when you do a find, there will be slashes in the index key box) If so that creates a different type of index from, say a character field index. It's possible that A5 may be handling the "Date" type of index improperly. I never use this form of an index, and perhaps that is why I've never seen what you are describing.

                              I suggest you change the index type by using an expression like

                              CDATE(datefield)

                              and then modifying your application accordingly to search for character values in the format of yyyymmdd.

                              I never use "Date" type indexes because you can never add another field to the expression without converting it to character anyway. Most of my indexes would be similar to the form of

                              CDATE(datefield)+ char_invoice_no

                              or similar. There are probably a few places where just the date field alone would be absolutely required (although I can't think what it would be), but by adding a linking field or similar, the index can often do double duty. What I mean by this is rather than having several indexes like

                              CDATE(datefield)
                              CDATE(datefield)+ char_invoice_no
                              CDATE(datefield)+ char_invoice_no+statuscode

                              I would just have

                              CDATE(datefield)+ char_invoice_no+statuscode

                              The exception to this is if you are using KEY_EXISTS() or DBSUM() and similar that require an exact key match. In most cases you can use TABLE_COUNT() and similar (Sorry I can't remember the table function names- I'm on the road) and not require the use of an exact key match, but be sure to specify the equations in the TABLE() functions so that LQO (Lightning Query Optimization) can be used, otherwise it will be alot slower.


                              Regards,

                              Ira J. Perlow
                              Computer Systems Design & Associates
                              [email protected]
                              Regards,

                              Ira J. Perlow
                              Computer Systems Design


                              CSDA A5 Products
                              New - Free CSDA DiagInfo - v1.39, 30 Apr 2013
                              CSDA Barcode Functions

                              CSDA Code Utility
                              CSDA Screen Capture


                              Comment

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