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  1. #1
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    access replication problems (xp)

    Here I am again with the same darn problem-- yesterday, in the middle of the Christmas project; the replica failed. We had had several "warnings" if you will. For the last week, for no reason the data base would lock up saying the the database was being used by another user and locked against changes. Then, yesterday it refused to sync with the other copies and when I finally decided to compact and repair to try to fix things-- it lost all the work for the day--but was able to recover about half with an append query-- I understand why only half appended but have no clue about why this all happened to begin with and am VERY worried about losing everything in the middle of the project-- almost 2000 children would not get gifts for Christmas. If anyone has a good idea to save this--or keep it stable until Christmas and then would really appreciate input on better ways to handle the whole datakeeping process for the center.

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    Re: access replication problems (xp)

    I just had a thought-- there are two computers in the network-- both users are doing data entry to the same database over the network-- the other computers are updated with a jumpdrive once a day. Could the problem be caused by the fact that there are two people using the database at once? WE do this all year long and it works fine but at Christmas there is continuous data entry for 10-18 hours a day. Maybe the program cant handle so many changes. If each of the people doing data entry had their own replica and did a sync once an hour it would be a bit inconvenient; but if it would save the data--it might be worth it. I wish I didnt have to come here bothering you guys but there is no one in my little town who can give me advice.

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    Re: access replication problems (xp)

    A couple things that you mention raise alarm bells:

    It is not clear whether you have split your application into frontend and backend components? Replication is appropriate ONLY for the backend (tables) portion of a split application. You must distribute the frontend to your networked computers using some other method .
    http://www.granite.ab.ca/access/splitapp/index.htm
    http://www.granite.ab.ca/access/autofe.htm

    Also, you mention a "jumpdrive". Not sure exactly what you mean, but if you are referring to a USB memory drive that is portable between computers, you are working on dangerous ground. Replicas MUST stay on the computer where they were created. Moving them between computers on any portable media such as USB drives, floppies, email, or ANY other media is an invitation to database corruption. If you are using a portable media, you must find a way to connect the remote computers to your network, even temporarily.

    http://www.trigeminal.com/usenet/usenet009.asp?1033


    Access and its replicated tables are OK for multi-user inputs.
    --------------------------------------------------
    Jack MacDonald
    Vancouver, Canada

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    Re: access replication problems (xp)

    There are a number of possible reasons for the locked message and it is impossible to tell what the reason might be from your description. What kind of locking scheme are you using in the database? With multiple user, the only practical scheme is No Locks, which is a misleading term since the records actually do get locked but not until they are updated.
    Charlotte

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    Re: access replication problems (xp)

    yes, front and back end databases-- replica is not moved from computer to computer-- one replica is on the usb removable drive and is sync'ed with the main computer and then with the other computers-- neither of which are used for data entry. Occasionally I need to work at home and then it is sync'ed with that one-- data is changed and added on the computer at home. The rest of the year, I have no problems with this arrangment.. but during November and December when many hundreds of changes are being made daily, the program stops working-- there is no other possible method of transferring the data. This is a very small non profit with extremely limited resources. (That would account for the fact that the director is also in charge of keeping the computers running LOL)

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    Re: access replication problems (xp)

    When you sync to the database on the usb removeable drive to the two (or three) different computers, that constitutes moving the replica. To you and me, the database hasn't been moved, but to the Jet database engine, it *has* been moved. Unfortunately, you just can't do that and expect the database to remain in a stable state.

    Here's what happens:
    - each replica stores the machinename and pathname of itself. It *knows* where it belongs
    - when you open the replica with Access/Jet, it compares the current environment (ie, the machine and pathname where it is currently running) with the "known" information contained within the replica
    - if they are found to be different, then it is considered to be a new replica
    - each new replica is tracked individually within the database
    - this happens *every* time that you open the database, whether or not you use the replica for data entry.


    To see for yourself, open your backend database and set the Tools > Options > View to show the Hidden and System objects, then look at a table called MSysReplicas (going by memory here!). It lists every replica in the set, and you will probably find many more than you were expecting. Until you use a supported method for sync'ing the replicas, you can expect to have problems.

    Any chance of using a notebook computer between the remote installations? If you sync'd to the notebook from both locations, then the replica will not be considered to be moved. There are other methods for doing remote sync's but it sounds like they may be beyond your financial reach.

    Wish I could be more positive, but that's the way it works.
    --------------------------------------------------
    Jack MacDonald
    Vancouver, Canada

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    Re: access replication problems (xp)

    Is replication the way to go here. How many tables need to be synchronised. When you take data home to add/change it are the 2 computers still adding/changing data while you have the database at home? If you can be sure they are not changing it while you are at home, then what is the point of replication. You could just copy the backend to take it home then replace the backend with the changed backend you have at home.

    Have you thought about recording the transactions on another database (not replicated) as a means of backup.

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    Re: access replication problems (xp)

    yes. I have done it both ways-- the reason for using the replication especially at this time of the year is so that I will not copy over the days data-- when you have worked 20 straight days for 16-20 hours a day; your brain starts to get a little mushy LOL-- and in the past, I once did wipe out a whole days work--and that was when we were only doing Christmas for about 1000! so it gets tricky. Here is the set up-- during the day-- at the back part of the building are two computers which are networked and where two people are continuously adding and changing data-- in the front of the building is another computer that needs the current information ( a read only version) but we are not able to network--so it is up dated daily. In another part of the big room in another computer that needs to have read only data but needs updated daily (or more often if we can get to it) At my house, a computer where I work nights until Thanksgiving and then I never leave the office-- I am about to take home 34 more requests to enter at home-- I did all the "new persons" part of it here-- the numbers for the people are assigned only at the office now that we are having so much trouble. If a laptop would be the way to save this, then we would have to consider that expense.

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    Re: access replication problems (xp)

    ok-- so now that I am at this point-- is my only option to use a laptop? Yes, many more replications than I was expecting. so why does this not cause a problem during the year? -- Actually, I would like that information later. For now, I need to figure a way to save this year-- and I dont think I have time to totally tear down the replication and put it back in a regular database. Anyone with a hint? I really need help [img]/forums/images/smilies/smile.gif[/img] As far as I know there is no easy way to take it from replication to not replicated-- I did it last February and it is way too time consuming.

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    Re: access replication problems (xp)

    Have you thought about a Wireless network, it doesn't cost much. Your only problem then is the copy you take home and enter data at home. All you need to do then is to either totally replace your backend at work with your backend from home (that was originally copied form the backend at work).

    How many tables are there to replicate?

    Are autonumbers a problems?

    Can you post a copy of the database so we can see if we can help in another way?

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    Re: access replication problems (xp)

    yep--have thought about it (wireless) but was advised against it so we have what we have-- as far as networking--at least for now. Well, automatic numbers are generated by the computer but not with autonumber exactly. There are seventeen tables and some rather large ones but you guys convinced me to bite the bullet before I had a major crash in the middle of the day with dozens of people trying to work and no computer [img]/forums/images/smilies/smile.gif[/img] I did all the make table queries this afternoon and will transfer them to another backend when I finish this-- then will spend the evening finding all the links that dont work and by tomorrow will have a stable database--BUT there are a few problems-- I had forgotten a few things. One, at the computer that I said was read only; there is a small amount of data being entered there-- it has to do with thank you notes and I think I will solve that one by setting up a totally different backend database for her and tie it to the screen she is already using-- what she doesn't know.... and then copy those tables to the whole database later-- I did that with another entry area and it works fine-- most of the volunteers are somewhat elderly and afraid of the computer so I have everything on a switchboard on their front end and everything they see is a report. No way for them to screw up the data. I guess the safest way to guard against this sleepy "elf" is to make two copies every day and then if I goof-- I can rescue myself with the second copy. One day when time is not so pressing, I would like some advice on making this project better. I live in a small town and I can't find anyone who know more about access than I do-- now that is scary! Thank you all for helping me think this one.through. BTW, Charlotte, all my "training" has come from your book and some by Woody.

  12. #12
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    Re: access replication problems (xp)

    >>I live in a small town and I can't find anyone who know more about access than I do-- now that is scary<<

    Not true, you have all the people at Woody's from all around the world.

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    Re: access replication problems (xp)

    My *guess* is what you said previously -- the amount of traffic at this time of year stresses the replication to a point that it can't cope because of the number of phantom replicas. But that's just a guess.

    I think there are two issues -- 1) how to get thru this season with the minimum disruption and 2) how to fix the problem long-term. Have a look at http://www.pacificdb.com.au/MVP/Code/UnReplicate.htm -- it's a nice utility for unreplicating a database. You should be able to unreplicate the database in its current state, create a new replica set, and then just carry on doing what you are currently doing. The number of phantom replicas will start again from zero, and you should/might be able to get thru the current season. It's a risk that you might need to take.

    For the longer term, the *right* answer is to implement Indirect Synchronization. It's a part of Replication Manager, a separate product that was included with the Office Developer's Edition in Access 97. Later versions of the Developer's Edition (under a different name), except for the Access 2003 version, also include Replication Manager. Setting it up to work properly is not trivial, but it's the only way (IMHO) to ensure stable synchronization over a remote connection.

    If that doesn't work for you, the notebook trick will work because both ends of your remote network will synchronize with the same replica on the notebook. It's a kludge, but may work for you.
    --------------------------------------------------
    Jack MacDonald
    Vancouver, Canada

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    Re: access replication problems (xp)

    and I do appreciate that! But I don't know enough to make a contribution here and I feel that I am a bother sometimes. After the holiday, I am going to see if there is someone who would help me think through ways to improve on what I now have-- United Way is asking for all agencies to gather data that is going to be hard to do and I can use all the help I can get.

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    Re: access replication problems (xp)

    I'm not contributing to this thread because I have no experience with replication, but let me assure you that you're not a bother at all. Your questions are always welcome, and there'll always be someone willing to try and help. <img src=/S/smile.gif border=0 alt=smile width=15 height=15>

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