should i advocate migrating from access to (my)sql_问答_开发者

We have a windows MFC app that is written against an access database on a company server. The db is not that big: 19 MB. There are at most 2-3 users accessing it at any one time. It is used in a factory environment where access speed (or lack thereof) over the intranet becomes noticeable as it is part of the manufacturing time for our widgets.

The scenario is this: as each widget is completed, it gets a record in the db.. by the end of the year, the db is larger and searching for a record takes longer and longer. The solution so far has been to manually move older records to an archival table about once a year.

We are reworking other portions of this app right now, and it would be a good time to move to another db if we are going to do it.

It is my understanding that if we were using sql, the search time would not go up as the table gets bigger because the entire .mdb does not have to be sent over the network each time. Is this correct? Does anyone have any insight about whether it could be worth it to go to the trouble (time and money) of migrating to a new db, or should I just add more functionality to the app开发者_StackOverflow中文版lication we have now, and maybe automatically purge the older records from time to time, and add additional facilities to the app to get at the older records when needed?

Thanks for any wisdom you can share..

Since your database is small and very few users, I could not make a solid case for migration. I would definetly set up an script to archive old records on a more frequent basis (don't archive into same db, this would somewhat defeat the purpose). But also make sure two things are correct as well.

INDEXES. If your queries start slowing down, make sure you have proper indexes http://support.microsoft.com/kb/304272
Your network connection between computers is fast. Maybe upgrade to gigabit cards and router? Possibly put the db on a scsi drive (raid 10 for speed and redundancy)

Throwing advanced technology at simple problems is an expensive way to go and not always the answer!

First of all, the information that the whole table and the whole database is transferred across the network is simply incorrect. If the queries are indexed, then the search times should not go up that much over time.

As others have mentioned spending the time + money to setup and maintain and then have someone maintain and manage and support that database server is certainly a possibility here. However, keep in mind that simply migrating a JET based application to sql server in many cases will run slower, and in fact sql server is slower then JET when no network is involved.

So, I would take some time to ascertain why things slow down so much, and also check into how indexing is setup.

So, just keep in mind that it is pure folklore and myth that the whole tables and whole database is transferred over the network. This concept is ONLY DUE to most people really not having any computer training and not knowing and understanding how the JET data engine works.

I would probably move to either Microsoft SQL Server 2008 R2 Express Edition (free) or MySQL (free) if there is both funding and time to put in a data access layer. Because you will be making requests of a remote server and not operating on data at the local workstation this move is very involved from the development standpoint.

However you should analyze whether or not its more cost effective to perform your archival process quarterly or monthly, and just move the archive database to SQL Server 2008 R2 Express Edition. (You can install the Microsoft SQL Server Management Studio client tools on workstations and query the archival database for faster reports on historical data without rewriting your entire production application; similar solutions exist for using MySQL or other OSS/free RDBMS).

I have cilents with 300 mb databases although they should be upsizing to SQL Server for other reasons. 19 Mb is relatively small. If performance is bad enough that archiving speeds things up then check the indexes to the tables for all your sorting and selection fields. Albert gave you a good URL there to check.

Entire MDB files do not go down the wire. Unless you are missing indexes.

Instead of shipping the DB over the network to the client and then performing queries, you could instead write a small wrapper on the server that handles requests, looks up the result in the Access DB (using SQL + the Access ODBC driver), and returns the result. This avoids the overhead of a large migration you might not need and still gets rid of the basic problem the users are experiencing.

Moving to a "proper" database solution is the best long term solution, but if your needs scale linearly and slowly over the next 30 years, it's hard to justify an expensive migration. That said, if you expect to really ramp up, or want to be more "future-proof", migrating now will likely save money/time.

It is my understanding that if we were using sql, the search time would not go up as the table gets bigger because the entire .mdb does not have to be sent over the network each time. Is this correct?

This general idea is true for almost all databases. The idea of a database is to separate your application from the actual data. The data resides in a database server. Your application doesn't.

Does anyone have any insight about whether it could be worth it to go to the trouble (time and money) of migrating to a new db

Yes. Having proposed this many times. It's expensive. It's complicated. Your MS-Access database will never get better or faster.

Other database servers will (and can) get faster and more sophisticated. After all, you're not sending .MDB files through a network anymore. The limitations are reduced. You're working with standard SQL through ODBC. Any database will work at the end of ODBC. You can fire vendors to find better, faster, cheaper products. Once you stop using Access you have choices.

Either stop using Access now or plan to suffer with it forever. And remake this decision every year until the end of time.