I have a MS Access 2013 file that I am using. There are two possibly related concerns. For some context, this is an MS Access 2013 file with some forms and some tables and a bit of VBA for the logic of how those two interact. For versioning, the file has been copied and pasted with a datestamp on it for the newer version.
The first concern is that all the file sizes for the various files is exactly the same, even though data has been added and some changes to the forms were made.
The second concern is that when I right click on a table and go to table properties, it says "Shortcut to Table (Local): table_name" where table_name is the name of the table. It appears that this is a shortcut to a table somewhere, but I'm not sure where. The forms are also shortcuts to forms, but I don't see the destination form in my file anywhere, even after unhiding system objects. My questions regarding this are: how did this happen (I was assuming it had something to do with the fact that I copied and pasted the file) and where is the file that these are a shortcut to?
Everything seems to work fine, but I'm concerned that if one of the legacy files gets removed that I might lose some data. Is my data being stored within this file, or did it get split somehow and the data is being stored in a different file somewhere? I just want to have a better grasp of what exactly is going on.
I feel like I have a good handle on the SQL and a pretty good grasp of the VBA, but the MS Access specific nuances are something I'm still gaining familiarity with.
Well, it seems it was as simple as changing the view in your navigation pane to something else than custom!
I am completely perplexed.
A colleague's got a database issue. I noticed that the (internal) software that created the local database file with the problem, uses programmatic access to MS JET, which meant an easy first step was to see if MS Access (2010) was happy with the database - and then fix, export/import or repair, as a first step.
I copied the stand-alone local Jet data file to a non-networked virtual machine (so no chance of external data), and MS Access opened the db file easily, but I can't make sense of what I'm seeing.
MS Access is configured on that system to show all hidden and system objects, confirmed since the Access system tables in the file are all visible and can be opened. These are my observations:
The object browser lists the usual MS system tables, and a bunch of SELECT queries (which look correct) of the form SELECT (FIELD LIST) FROM (OTHERTABLENAME) WHERE (FIELDNAME=VALUE), nothing more.
The select queries show the usual grid with valid data records when opened, and the data looks correct as well.
No data tables with the given names are showing in the object browser interface.
The given names are listed as objects of the database, in the system table MSysObjects.
So..... the underlying data tables ARE named in MSysObjects, and seem to be true data tables... but they are NOT being listed in the object browser and I can't figure how to open their datasheets (although MS Access' system tables are, and "Show hidden/system" are both enabled)... and the tables surely do exist in the file since an apparent SELECT query is pulling their data from them, and the file is on a clean non-networked machine with no other sources reachable.
Any ideas? I want to check the underlying data but ... whats going on?
When I examined your database, I discovered the reason you can't access the tables normally is because the authors of the internal application which created the db file implemented measures to prevent normal access.
I advise you to contact them and your managers to get authorization and assistance to view the data.
Also, please be cautious with this question. A suspicious person might uncharitably interpret your question as a disguised request for hacking help. Please note I am not accusing you of anything underhanded ... simply asking you to notice how your question might be perceived. And, if that were to happen, I don't know what the consequences would be on Stack Overflow, but I can't imagine it would be good. So please be careful.
i have 2 questions when i use access:
i create a form with comboBox and calenders, i want to choose an employee
from combobox and from date and to date and when i click ok i will send these
parameters to a query to return the result in a query (result is the calculation
of it's salary).
i know how to release an access project to be useful to user that can't
access tables and queries only forms.
is there any way to change the access project from release mode to development
one, because supposed that an error occurred, how to solve it without loosing
my data.
Note: i don't have client/server i develop a program and i release it and
give this release to the user, after a specific time this user tell me that
an error occurred, and he need data inserted from this program to database.
i can solve this problems and release another version of program, but the
main problem is how to take all data from the old program to the new one.
-- You can reference form control in a query:
SELECT FROM MyTable
WHERE EmployeeID = Forms!MyForm!cboEmployee
AND SomeDate BETWEEN Forms!MyForm!txtDateStart And Forms!MyForm!txtDateEnd
You could also build an SQL string and use it as the record source for a form or in VBA.
-- Access should be split into front-end (forms, reports, etc) and back-end (data). When you make changes to the front-end, you create a new mde or accde and send that to the users. The data stays on a server in the back-end.
See: http://msdn.microsoft.com/en-us/library/aa167840(v=office.11).aspx
EDIT
From your comments, it seems that each application has a single user, if this is the case, splitting is not essential, but it can still be a good idea. The user will get two databases, one for data and one for forms etc and only the one for forms gets replaced. You will need to include a routine to locate and link the back-end tables.
However, if this is not possible, an mde or accde does not hide the data, you can send your revised copy and include a routine to import from the previous mde/accde.
EDIT 2
There are wizards that will split your database for you and link the tables. Where you find them varies slightly from version to version, but they are under the menu item Database Tools. The only problem with this is that the linked table holds the location for the back-end, which is on your computer, not on your users computer. Linked tables are how you access data in the second database. These act as if there are tables in the first database, except you cannot change them. Unfortunately, linked tables hold the location of the back-end, so this will have to be changed if you are sending it to a users. You can either write code, or show your user how to use the linked table manager. This may lead to confusion and may not be worth the effort for one PC. (See also http://www.alvechurchdata.co.uk/accsplit.htm)
Alternatively, you can split the database on your PC and make all the changes to forms etc that you want, then add some code that will import the tables and other data for the user into your new copy. The user will follow the instructions in your code to import the tables. As an aside, you will find that development is a lot safer on a split database. You should also decompile from time to time, which you can find at http://www.granite.ab.ca/access/decompile.htm.
If you want to protect your code, you can create a compiled version of this new copy, the extension for a compiled Access database is *.accde, for 2007 onward and *.mde for prior versions. This is what I thought you meant by 'i know how to release an access project'.
How can I track changes to a development database and apply those changes to a production database (SQL Server 2008)?
I keep a local copy of a database on my development server, and as I'm adding new features, I may add new tables or change field and table names in the database. What's a good way to track such changes and then apply them to the main database?
Is there some way to do a "diff"-like operation between two databases and merge definition changes?
I considered merge-replication, but I'm not sure how well than handles schema changes. For example, here: http://technet.microsoft.com/en-us/library/ms151870.aspx it mentions that I basically cannot use SSMS to make definition changes, because it drops and recreates tables, which is not allowed for published objects.
A smart piece of software could compare column counts, types, positions, and apply other fuzzy matching/logical deduction methods to figure out that a table was renamed or a new table was added or a column name changed, after which it could present the differences to the user for confirmation and automatic application.
Does anything like what I've described above exist, or am I stuck remembering to save DDL statements in SSMS and running them manually in the production database?
Maybe you need a migration tool like (for example) FluentMigrator, which helps you track database changes in source code.
Here is a tutorial from the original author of Fluent Migrator, explaining what Fluent Migrator is, why you might need it and how it works.
Another alternative would be what you already mentioned:
A smart piece of software could compare column counts, types,
positions, and apply other fuzzy matching/logical deduction methods to
figure out that a table was renamed or a new table was added or a
column name changed, after which it could present the differences to
the user for confirmation and automatic application.
I never tried it myself, but I've seen lots of recommendations for Redgate SQL Compare (which apparently does exactly what you asked for) here at Stack Overflow.
I have created an MS Access 2003 application, set up as a split front-end/back-end configuration, with a user group of about five people. The front end .mdb sits on a network file server, and it contains all the queries, forms, reports, and VBA code, plus links to all the tables in the back end .mdb and some links to ODBC data sources like an AS/400. The back end sits on the same network file server, and it just has the table data in it.
This was working well until I "went live" and my handful of users started coming up with enhancement requests, bug reports, etc. I have been rolling out new code by developing/testing in my own copy of the front-end .mdb in another network folder (which is linked to the same back-end .mdb), then posting my completed file in a "come-and-get-it" folder, alerting the users, and they go copy/paste the new front-end file to their own folders on the network. This way, each user can update their front end when they're at a 'stopping point' without having to boot everyone out at once.
I've found that when I'm developing now, sometimes Access becomes extremely slow. Like, when I am developing a form and attempt to click a drop-down on the properties box, the drop-down arrow will push in, but it will take a few seconds before the list of options appears. Or there's tons of lag in selecting & moving controls on a form. Or lots of keyboard lag.
Then, at other times, there's no lag at all.
I'm wondering if it's because I'm linked to the same back end as the other users. I did make a reasonable effort to set up the queries, forms, reports etc. with minimal record locking, if any at all, depending on the need. But I may have missed something, or perhaps there is some other performance issue I need to address.
But I'm wondering if there is an even better way for me to set up my own development back-end .mdb, so I can be testing my code on "safe" data instead of the same live data as the rest of the users. I'm afraid that it's only a matter of time before I corrupt some data, probably at the worst possible moment.
Obviously, I could just set up a separate back-end .mdb and manually reconfigure the table links in the front end every time, using the Linked Table Manager. But I'm hoping there is a more elegant solution than that.
And I'm wondering if there are any other performance issues I should be considering in this multi-user, split database configuration.
EDIT: I should have added that I'm stuck with MS Access (not MS-SQL or any other "real" back end); for more details see my comment to this post.
If all your users are sharing the front end, that's THE WRONG CONFIGURATION.
Each user should have an individual copy of the front end. Sharing a front end is guaranteed to lead to frequent corruption of the shared front end, as well as odd corruptions of forms and modules in the front end.
It's not clear to me how you could be developing in the same copy of the front end that the end users are using, since starting with A2000, that is prohibited (because of the "monolithic save model," where the entire VBA project is stored in a single BLOB field in a single record in one of the system tables).
I really don't think the problems are caused by using the production data (though it's likely not a good idea to develop against production data, as others have said). I think they are caused by poor coding practices and lack of maintainance of your front end code.
turn off COMPILE ON DEMAND in the VBE options.
make sure you require OPTION EXPLICIT.
compile your code frequently, after every few lines of code -- to make this easy, add the COMPILE button to your VBE toolbar (while I'm at it, I also add the CALL STACK button).
periodically make a backup of your front end and decompile and recompile the code. This is accomplished by launching Access with the /decompile switch, opening your front end, closing Access, opening your front end with Access (with the SHIFT key held down to bypass the startup code), then compacting the decompiled front end (with the SHIFT key held down), then compiling the whole project and compacting one last time. You should do this before any major code release.
A few other thoughts:
you don't say if it's a Windows server. Linux servers accessed over SAMBA have exhibited problems in the past (though some people swear by them and say they're vastly faster than Windows servers), and historically Novell servers have needed to have settings tweaked to enable Jet files to be reliably edited. There are also some settings (like OPLOCKS) that can be adjusted on a Windows server to make things work better.
store your Jet MDBs in shares with short paths. \Server\Data\MyProject\MyReallyLongFolderName\Access\Databases\ is going to be much slower reading data than \Server\Databases. This really makes a huge difference.
linked tables store metadata that can become outdated. There are two easy steps and one drastic one to be taken to fix it. First, compact the back end, and then compact the front end. That's the easy one. If that doesn't help, completely delete the links and recreate them from scratch.
you might also consider distributing an MDE to your end users instead of an MDB, as it cannot uncompile (which an MDB can).
see Tony Toews's Performance FAQ for other generalized performance information.
1) Relink Access tables from code
http://www.mvps.org/access/tables/tbl0009.htm
Once I'm ready to publish a new MDE to the users I relink the tables, make the MDE and copy the MDE to the server.
2) I specifically created the free Auto FE Updater utility so that I could make changes to the FE MDE as often as I wanted and be quite confident that the next time someone went to run the app that it would pull in the latest version. For more info on the errors or the Auto FE Updater utility see the free Auto FE Updater utility at http://www.granite.ab.ca/access/autofe.htm at my website to keep the FE on each PC up to date.
3) Now when working on site at a clients I make the updates to the table structure after hours when everyone is out of the system. See HOW TO: Detect User Idle Time or Inactivity in Access 2000 (Q210297) http://support.microsoft.com/?kbid=210297 ACC: How to Detect User Idle Time or Inactivity (Q128814) http://support.microsoft.com/?kbid=128814
However we found that the code which runs on the timer event must be disabled for the programmers. Otherwise weird things start happening when you're editing code.
Also print preview would sometimes not allow the users to run a menu item to export the report to Excel or others. So you had to right click on the Previewed report to get some type of internal focus back on the report so they could then export it. This was also helped by extending the timer to five minutes.
The downside to extending the timer to five minutes was if a person stays in the same form and at the same control for considerable parts of the day, ie someone doing the same inquiries, the routine didn't realize that they had actually done something. I'll be putting in some logic sometime to reset this timer whenever they do something in the program.
4) In reference to another person commenting about scripts and such to update the schema see Compare'Em http://home.gci.net/~mike-noel/CompareEM-LITE/CompareEM.htm. While it has its quirks it does create the VBA code to update tables, fields, indexes and relationships.
Use VBA to unlink and re-link your tables to the new target when switching from dev to prod. It's been to many years for me to remember the syntax--I just know the function was simple to write.
Or use MS-Access to talk to MS-Access through ODBC, or some other data connection that lives outside of the client mdb.
As with all file base databases, you will eventually run into problems with peak usage or when you go over a small magical number somewhere between 2 and 30.
Also, Access tends to corrupt frequently, so backup, compact and repair need to be done on an frequent basis. 3rd party tools used to exist to automate this task.
As far as performance goes, the data is being processed client side, so you might want to use something like netmeter to watch how much data is going over the wire. The same principle about indexing and avoiding table scans apply to file base dbs as well.
Many good suggestions from other people. Here's my 2 millicents worth. My backend data is on server accessed through a Drive mapping. In my case, the Y drive. Production users get the mapping through a login script using active directory. Then the following scenarios are easily done by batch file:
Develop against local computer by doing a subst command in a batch file
run reports against last nights data by pointing Y to the backup server (read only)
run reports against end of month data by pointing to the right directory
test against specialized scenarios by keeping a special directory
In my environment (average 5 simultaneous users, 1000's of rows, not 10,000's.) corruption has occurred, but it's rare and manageable. Only once in the last several years have we resorted to the previous days backup. We use SQL Server for our higher volume stuff, but it's not as convenient to develop against, probably because we don't have a SQL admin on site.
You might also find some of the answers to this question (how to extract schemas from access) to be useful as well. Once you've extracted a schema using one of the techniques that were suggested you gain a whole range of new options like the ability to use source control on the schemas, as well as being able to easily build "clean" testing environments.
Edit to respond to comment:
There's no easy way to source control an Access database in it's native format, but schema files are just text files like any other. Hence, you can check them in and out of the source control software of your choice for easy version control/rollbacks.
Or course, it relies on you having a series of scripts set up to re-build your database from the schema. Once you do, it's normally fairly trivial to create an option/alternative version that rebuilds it in a different location, allowing you to build test environments from any previous committed version of the schema. I hope that clarifies a bit!
If you want to update the back end MDB schema automatically when you release a new FE to the clients then see Compare'Em http://home.gci.net/~mike-noel/CompareEM-LITE/CompareEM.htm will happily generate the VBA code need to recreate an MDB. Or the code to create the differences between two MDBs so you can do a version upgrade of the already existing BE MDB. It's a bit quirky but works.
I use it all the time.
You need to understand that a shared mdb file for the data is not a robust solution. Microsoft would suggest that SQL Server or some other server based database would be a far better solution and would allow you to use the same access front end. The migration wizard would help you make the changeover if you wanted to go that way.
As another uses pointed out, corruption will occur. It is simply a question of how often, not if.
To understand the performance issues you need to understand that to the server the mdb file with the data in it is simply that, a file. Since no code runs on the server, the server does not understand transactions, record locking etc. It simply knows that there is a file that a bunch of people are trying to read and write simultaniously.
With a database system such as SQL Server, Oracle, DB2. MySQL etc. the database program runs on the server and looks to the server like a single program accessing the database file. It is the database program (running on the server) that handles record locking, transactions, concurrency, logging, data backup/recovery and all the other nice things one wants from a database.
Since a database program designed to run on the server is designed to do that and only that, it can do it far better and more efficently that a program like Access reading an writing a shared file (mdb).
There are two rules for developing against live data
The first rule is . . . never develop
against live data. Not ever.
The second rule is . . .never develop
against live data. Not ever.
You can programatically change the bindings for linked tables, so you can write a macro to change your links when you're deploying a new version.
The application is slow because it's MS Access, and it doesn't like many concurrent users (where many is any number > 1).