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 application 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.
Related
We have a 3gb file of data from our propriartary CRM system which is using SQL as a database.
The CRM is not meeting our needs and we are thinking about moving to Microsoft access and building our own system from the start.
We were wondering if it is possible to easily migrate the SQL database into access?
Thanks for your time.
First of all, it has been a long time since I've had to use MS-Access (thankfully) but I'm not sure Access is suitable for databases of that size. In my opinion, it's best suited to small, desktop-type applications with few concurrent users.
To answer your question, I believe Access offers a data import feature(see under the External Data ribbon in 2013) - though I'd suspect it might balk at the idea of 3GB of data. Edit: Actually this link suggests the max databsae size is 2GB
What might be more useful however, is its Linked Table feature. If I remember correctly this allows you to access data stored in SQL Server (or a similar RDBMS) which is more suited to large volumes of data through an Access front end - complete with pre-canned forms, queries, reports etc..
It is possible and fairly straight forward to move all of your data tables from SQL Server to Access; however, SQL Server is a much more robust database engine than Access. I would highly recommend against that. I have however had very good success using Access (ADP project files) as a front for the interface and using SQL Server as the database back-end for simple to moderate complexity interfaces. If you are not getting the performance you desire from your SQL Server, you might want to consider query performance tuning and looking into memory and hardware upgrades first. I think you will get better and faster results from doing that.
The simple solution would be to “link” Access to SQL server. That way you continue to use a robust data engine, but are free to use all the reporting and coding features of Access.
In this setup then Access simply becomes a “front end” to the existing SQL database.
And you do NOT want to use an ADP project in Access since they are depreciated.
The process is thus to create a blank standard database, and then use linked tables to SQL server. This will not only eliminate the need to import data (which is likely changing all the time).
This question is quite general, however, i can not find a good answer for it.
What are the possibilities for using an external database with MS Access?
I see that MySQL can be used, but I would have to setup a ODBC connection and install drivers on every machine. The issue is that I have a software developed in MS Access that uses a lot of data, and it gets very slow at processing the data when i include a lot of data.
The software analyzes data from wind turbines, so it is used by different customers and it may contain a lot of different turbines with 50,000+ rows in each data set.
I would like these turbine data to be stored in a separate file that is pointed to by MS Access, so I include the software + whatever turbine data wanted.
As it is now, i have a lot of Access database files where the data is included in the software. It becomes impossible to keep track of - Especially when I do an edit to the source code of the software, which is do a lot these days.
Another issue is that the users may only have Access Runtime.
What are my options here? Is the best method to use the Access Link function?
Best regards, Emil.
Edit:
SQL's - Can they be combined? :
SELECT q_DataLimited.YAW001, q_DataLimited.YAW002
FROM q_DataLimited
WHERE (((q_DataLimited.YAW002)>Degree_dsp() And (q_DataLimited.YAW002)<Degree_dsp_high()));
And
SELECT Count(q_WindRose_PCU.YAW001) AS CountOfYAW0011
FROM q_WindRose_PCU;
Edit 2:
Public Degree As Long
Public Function Degree_dsp() As Long
Degree_dsp = Degree * 20
End Function
I have the degree as a counter outside the function in a form being:
For Degree = 0 To 17
DoCmd.OpenQuery "q_WindRose_PCU"
DoCmd.Close
Next Degree
Edit 3:
How to combine a query and the append of it to a table?
SELECT q_PowerBinned.Bin, Avg(q_PowerBinned.POW001) AS AvgOfPOW001, StDev(q_PowerBinned.POW001) AS StDevOfPOW001, Avg(q_PowerBinned.WSP001) AS AvgOfWSP001, StDev(q_PowerBinned.WSP001) AS StDevOfWSP001, Avg(q_PowerBinned.POW002) AS AvgOfPOW002, StDev(q_PowerBinned.POW002) AS StDevOfPOW002, Avg(q_PowerBinned.WSP002) AS AvgOfWSP002, StDev(q_PowerBinned.WSP002) AS StDevOfWSP002, Count(q_PowerBinned.Bin) AS CountOfBin
FROM q_PowerBinned
GROUP BY q_PowerBinned.Bin;
And then the append of the above to a table:
INSERT INTO t_Average_Stored ( Bin, PowAvg001, WindAvg001, PowAvg002, WindAvg002, n_samples, PowDev001, WindDev001, PowDev002, WindDev002 )
SELECT q_Average_Temp.Bin, q_Average_Temp.AvgOfPOW001, q_Average_Temp.AvgOfWSP001, q_Average_Temp.AvgOfPOW002, q_Average_Temp.AvgOfWSP002, q_Average_Temp.CountOfBin, q_Average_Temp.StDevOfPOW001, q_Average_Temp.StDevOfWSP001, q_Average_Temp.StDevOfPOW002, q_Average_Temp.StDevOfWSP002
FROM q_Average_Temp;
I see already a few suggestions in the comments, but I am going to answer the general question you posted. In short, the possibilities are endless.
MS Access, and Excel for that matter, have excellent external data tools that allow you to connect to almost any external data source and leverage on regular SQL-based databases or even use OLAP cubes to do your analysis. Access itself should be powerful enough to handle the data sets you mention. Even Access 2010 should be able to handle millions of records with relative ease.
MS Access does have a significant limitation, which is the 2GB file size. Once your database reaches 2GB, everything goes out the window and you are very likely to get data corruption. This is a well known issue, but I don't think you are anywhere near these limits.
Before considering an upgrade, though, there are a few things to suggest:
Analyze the structure of your data and your database. Perhaps your tables are too big (lots of columns) and unnecessarily redundant. It may make sense to process the raw data you receive to split it into different tables that reduce the redundancy and improve performance.
Look into indexing some key fields in your tables. This is heavily dependent on the type of analysis you do and what queries are most common. Read up on indexes and how to use them and explore some options with actual datasets. You may be surprised how queries that used to take minutes to run become almost instantaneous when the right indexes are created and maintained.
Analyze your queries for performance. If I remember correctly, MS Access 2010 had a performance analyzer, which could improve your queries to make them run more efficiently.
If you have already looked into the items above and you decide you really need to take a step up, one fairly easy path (and inexpensive) is to install SQL Server Express, which you can download for free from Microsoft. Access was made to talk to SQL Server and the performance is many times better. You can run SQL Server Express in your personal pc and use it as a back-end for Access, or you could actually install it in a networked pc and use it as a server (behind a firewall, of course, NEVER connected to the Internet). In this setup you can access your data from several PCs.
One key thing to keep in mind once you start using Access as a front end, is that you want to push the processing to the back end, not keep it in Access. The best way to do this is to create what Access calls pass-through queries. These queries are written in the backend's native SQL language and are sent to the back end server for processing. Only the processed data comes back. If you don't do this, for example by creating the queries in the visual editor in Access instead, the raw data will be sent to Access and then Access will try to create your results. This, as you can imagine, can actually be a lot slower than your initial situation, so don't do it.
If you are not a SQL expert and need a visual editor, there is a tool that you can download from Microsoft: SQL-Server Management Studio Express. The query editor is not that different from Access and will allow you to create queries in a visual manner, but in Transact-SQL (the language of SQL Server). You can also manage your SQL Server Express with this tool and maintain your data in this manner (import, export, etc). You can create the SQL statements you need in this editor and then copy and paste into the pass-through queries in Access. The data will be available for you in the program you are familiar with, but with the power of a much bigger database engine behind the scenes.
Since I do not want to sound like a Microsoft shill, I definitely want to mention other options for external data that could be equally or even more powerful than SQL Server Express. The only reason I mentioned these is because you are already familiar with Microsoft products and the learning curve is a bit less steep. Also, most things should work together out of the box.
The first option that comes to mind is SQLite, which is a high performing database that is actually file-based. It is very small, yet very powerful and fast, and it is ideal for a locally based application like what you mention. There are also lots of graphical interfaces for SQLite and you can connect to it via ODBC from Access. Again, you want to run everything using pass-through queries and let SQLite pick up the load. SQLite is Open Source and it is free.
If you are keen on having "a real database server", then MySQL is probably the next step up. Also Open Source and free, it is very popular, which means lots of places to get support and different graphical interfaces to choose from.
Any search for Open Source Database will give you even more options to try and choose from.
One key thing to keep in mind: if you install any database server in your PC, it will become a server, and will start advertising its services in your local network or on the internet if you bring it to a local Starbucks. Be careful with that, learn how to start/stop the services in your PC, and make sure you turn them off when you are not behind a firewall. There are many exploits for different database servers and you will get quickly detected once your PC starts advertising its newly acquired abilities.
Just to close, there is no difference in the performance of Access and the runtime. Just the ability to edit the queries and so on. Whatever front end you create in Access, your users will be able to utilize in the same manner.
We have an AS400 mainframe running our DB2 transactional database. We also have a SQL Server setup that gets loaded nightly with data from the AS400. The SQL Server setup is for reporting.
I can link the two database servers, BUT, there's concern about how big a performance hit DB2 might suffer from queries coming from SQL Server.
Basically, the fear is that if we start hitting DB2 with queries from SQL Server we'll bog down the transactional system and screw up orders and shipping.
Thanks in advance for any knowledge that can be shared.
Anyone who has a pat answer for a performance question is wrong :-) The appropriate answer is always 'it depends.' Performance tuning is best done via measure, change one variable, repeat.
DB2 for i shouldn't even notice if someone executes a 1,000 row SELECT statement. Take Benny's suggestion and run one while the IBM i side watch. If they want a hint, use WRKACTJOB and sort on the Int column. That represents the interactive response time. I'd guess that the query will be complete before they have time to notice that it was active.
If that seems unacceptable to the management, then perhaps offer to test it before or after hours, where it can't possibly impact interactive performance.
As an aside, the RPG guys can create Excel spreadsheets on the fly too. Scott Klement published some RPG wrappers over the Java POI/HSSF classes. Also, Giovanni Perrotti at Easy400.net has some examples of providing an Excel spreadsheet from a web page.
I'd mostly agree with Buck, a 1000 row result set is no big deal...
Unless of course the system is looking through billions of rows across hundreds of tables to get the 1000 rows you are interested in.
Assuming a useful index exists, 1000 rows shouldn't be a big deal. If you have IBM i Access for Windows installed, there's a component of System i Navigator called "Run SQL Scripts" that includes "Visual Explain" that provides a visual explanation of the query execution plan. View that you can ensure that an index is being used.
On key thing, make sure the work is being done on the i. When using a standard linked table MS SQL Server will attempt to pull back all the rows then do it's own "where".
select * from MYLINK.MYIBMI.MYLIB.MYTABE where MYKEYFLD = '00335';
Whereas this format sends the statement to the remote server for processing and just gets back the results:
select * from openquery(MYLINK, 'select * from mylib.mytable where MYKEYFLD = ''00335''');
Alternately, you could ask the i guys to build you a stored procedure that you can call to get back the results you are looking for. Personally, that's my preferred method.
Charles
I'm in a satellite office that needs to pull some data from our main office for display on our intranet. We use MS SQL Server in both locations and we're planning to create a linked server in our satellite office pointing to the main office. The connection between the two is a VPN tunnel I believe (does that sound right? What do I know, I'm a programmer!)
I'm concerned about generating a lot of traffic across a potentially slow connection. We will be getting access to a SQL view on the main office's server. It's not a lot of data (~500 records) once the select query has run, but the view is huge (~30000 records) without a query.
I assume running a query on a linked server will bring back only the results over the wire (and not the entire view to be queried locally). In that case the major bottleneck is most likely the connection itself assuming the view is indexed, etc. Are there any other gotchas or potential bottlenecks (maybe based on the way I structure queries) that I should be aware of?
From what you explained your connection is likely to be the bottleneck.
Also, you might also consider caching data at the satellite location.
The decision will depend on the following:
- how many rows and how often data are updated in the main database
- how often you need to load the same data set at satellite location
Two edge examples:
Data is static or relatively static - inserts only in main DB. In satellite location users often query the same data again and again. In this case it would make sense to cache the data locally at satellite location.
Data is volatile, a lot of updates or/and deletes. Users in satellite location rarely query data and when they do, it is always different where condition. In this case it doesn't make sense to cache. If connection is slow and there are often changes you might end up never being at sync with the main DB.
Another advantage of caching is that you can implement data compression, which will alleviate bad effect of slow connection.
If you chose to cache at local location there are a lot of options, but this I believe would be another topic.
[Edit]
About compression: You can use compressed transaction log shipping. In SQL 2008 compression is supported in Enterprise edition only. In SQL 2008 R2 it is available starting Standard version. http://msdn.microsoft.com/en-us/library/bb964719.aspx .
You can implement custom compression before you ship transaction logs, using any compression library you like.
I'm considering undertaking a project to migrate a very large MS Access application to a new system based on SQL Server. The existing system is essentially an ERP application with a couple of dozen users, all sharing the Access database over the network. The database has around 300 tables and lots of messy VBA code. This system is beginning to break down (actually, it's amazing it has worked as long as it has).
Due to the size and complexity of the Access application, a 'big bang' approach is not really feasible. It seems sensible to rope off chunks of functionality and migrate them piecemeal to the new system. During the migration process, which I expect to take several months, there may be a need for both databases to be in operation and be able to query and modify data in both systems.
I have considered using something like the ADO.NET Entity Framework to implement a data abstraction layer to handle this, but as far as I can tell, the Entity Framework has no Access provider.
Does my approach seem reasonable? What other strategies have people used to accomplish similar goals?
You may find that the main problem is using the MS Access JET engine as the backend. I'm assuming that you do have an Access FE (frontend) with all objects except tables, and a BE (backend - tables only).
You may find that migrating the data to SQL Server, and linking the Access FE to that, would help alleviate problems immediately.
Then, if you don't want to continue to use MS Access as the FE, you could consider breaking it up into 'modules', and redesign modules one by one using a separate development platform.
We faced a similar situation a few years ago, but we knew from the beginning that we'll have to swich one day to SQL SERVER, so the whole code was written to work from an Access client to both Access AND SQL server databases.
The idea of having a 'one-step' migration to SQL server is certainly the easier way to manage this on the database side, and there are many tools for that. But, depending on the way your client app talks to the database, your code might then not work properly. If, for example, your code includes a lot of SQL instructions (or generates them on the fly by, for example, adding filters to SELECT instructions), your syntax might not be 'SQL server' compatible: access wildcards, dates, functions, will not work on SQL server.
In addition to this, and as said by #mjv, the other drawback of a one time switch to MS SQL is that you will inheritate many of the problems from the original database: wrong or inapropriate field names, inapropriate primary/foreign key policies, hidden one-to-many relations that you'd like to implement in the new database model, etc.
I'll propose here some principles and rules to implement a 'soft transition' solution, which clearly best fits you. Just to say that it's not going to be easy, but it's definitely very interesting, paticularly when dealing with 300 tables! Lucky you!
I assume here that yo have the ability to update the client code, and you'd prefer to keep at all times the same client interface. It is of course possible to have at transition time two different interfaces, one for each database, but this will be very confusing for the users, and a permanent source of frustration for them.
According to me, the best solution strongly depend on:
The original connection technology,
and the way data is managed in your
client's code: Access linked tables,
ODBC, ADODB, recordset, local
tables, forms recordsources, batch
updating, etc.
The possibilities to split your
tables and your app in 'mostly
independant' modules.
And you will not spare the following mandatory activities:
setup up of a transfer
procedure from Access database to SQL server. You
can use already existing tools (The
access upsizing wizard is very poor,
so do not hesitate to buy a real
one, like SSW or EMS SQL Manager,
very powerfull) or build your own
one with Visual Basic. If your plan
is to make some changes in Data
Definition, you'll definitely have
to write some code. Keep in mind
that you will run this code
maaaaaany times, so make sure that
it includes all time-saving
instructions that will allow you to
restart the process from the start
as many times as you want. You will
have to choose between 2 basic data
import strategies when importing data:
a - DELETE existing record, then INSERT imported record
b - UPDATE existing record from imported record
If you plan to switch to new Primary\foreign key types, you'll have to keep track of old identifiers in your new database model during the transition period. Do not hesitate to switch to GUID Primary Keys at this stage, especially if the plan is to replicate data on multiple sites one of these days.
This transfer procedure will be divided in modules corresponding to the 'logical' modules defined previously, and you should be able to run any of these modules independantly (keeping of course in mind that they'll probably have to be implemented in a specific order, where the 'customers' module has to run before the 'invoicing' module).
implement in your client's code the possibility to connect to both original ms-access database and new MS SQL server. Ideally, you should be able to manage from within your code both connections for displaying and validating data.
This possibility will be implemented by modules, where you will have, for each of them, a 'trial period', ie the possibility to choose at testing time between access connection and sql connection when using the module. Once testing is done and complete, the module can then be run in exclusive SQL server mode.
During the transfer period, that can last a few months, you will have to manage programatically the database constraints that exist between 'SQL server' modules and 'Access' modules. Going back to our customers/invoicing example, the customers module will be first switched to MS SQL. Before the Invoicing module can be switched, you'll have to implement programmatically the one to many relations between Customers and Invoices, where each of the tables will be in a different database. Such a constraint can be implemented on the Invoice form by populating the Customers combobox with the Customers recordset from the SQL server.
My proposal is to build your modules following your database model, allways beginning with the 'one' tables or your 'one-to-many' relations: basic lists like 'Units', 'Currencies', 'Countries', shall be switched first. You'll have a first 'hands on' experience in writting data transfer code, and managing a second connection in your client interface. You'll be then able to 'go up' in your database model, switching the 'products' and 'customers' tables (where units, countries and currencies are foreign keys) to the new server.
Good luck!
I would second the suggestion to upsize the back end to SQL Server as step 1.
I would never go to the suggested Step 2, though (i.e., replacing the Access front end with something else). I would instead suggest investing the effort in fixing the flaws of the schema, and adjusting the Access app to work with the new schema.
Obviously, it is never the case that everything just works hunky dory when you upsize -- some things that were previously quite fast will be dogs, and some things that were previously quite slow will be fast. And I've found that it is often the case that the problems are very often not where you anticipate that they will be. You can only figure out what needs to be fixed by testing.
Basically, anything that works poorly gets re-architected, or moved entirely server-side.
Leverage the investment in the existing Access app rather than tossing all that out and starting from scratch. Access is a fine front end for a SQL Server back end as long as you don't assume it's going to work just the same way as it would with a Jet/ACE back end.
...thinking out loud... I think this may work.
I appears that the complexity of the application resides in the various VBA modules rather than the database table/schema themselves. A possible migration path could therefore be to first migrate the data storage to SQL server, exactly as-is, as follow:
prevent any change to the data for a few hours
duplicate all tables to the SQL server; be sure to create the same indexes as well.
create linked tables to ODBC Source pointing to the newly created tables on SQL Server
these tables should have the very same name as the original tables (which therefore may require being renamed, say with a leading underscore, for possible reference).
Now, the application can be restarted and should be using the SQL tables rather than the Access tables. All logic should work as previously (right...), possible slowness to be expected, depending on the distance between the two machines.
All the above could be tested in about a day's work or so; the most tedious being the creation of the tables on SQL server (much of that can be automated, I'm sure). The next most tedious task is to assert that the application effectively works as previously, but with its storage on SQL.
EDIT: As suggested by a comment, I should stress that there is a [fair ?] possibility that the application would not readily work so smoothly under SQL server back-end, and could require weeks of hard work in testing and fixing. However, and unless some of these difficulties can be anticipated because of insight into the application not expressed in the question, I propose that attempting the "As-is" migration to SQL Server should be considered; after all, it may just work with minimal effort, and if it doesn't, we'd know this very quickly. This is therefore a hi-return, low risk proposal...
The main advantage sought with this approach is that there will be a single storage during the [as the OP expects] longer period during which the old Access application will co-exist with the new application.
The drawback of this approach, is that, at least at first, the schema of original database is reproduced verbatim, i.e. including some of its known quirks and legacy-herited idiosyncrasies. These schema issues (and the underlying application logic) can be in time corrected, but this is of course less easy than if the new application starts ab initio, with its own, separate, storage, and distinct schema.
After the storage is moved to SQL server, the most used and/or the most independent modules of the Access application can be re-written in the new application, and as significant portions of the original application is ported, effective usage, by select beta testers or by actual users can start to be switched to the new application.
Possibly, some kind of screen-scraping based logic or some other system could be used to produce an hybrid application which would provide the end users with a comprehensive application, which sometimes work from new logic, and sometimes from the original MS-Access program.