Data Corruption

[Pilotwings_64]

I’m building a very big database in access and I’m concerned about data corruption. So let’s say that I enter a record today and it gets corrupted today. Will Access recognize this immediately so I can deal with it, or will that record remain unnoticed until I try to pull up the information and actually see that the data is corrupt?

Thanks.

[ajetrumpet]

you will not know about corruption until the signs show up. And they could be anything. The only way to detect it really is to start witnessing things that happen in a database that are not logical. Kind of the way that astronomers detect black holes. They can't find them until they see a star massively speed up for no reason.

What you can do to stop this though is make a backup of your file everyday, say when you open it. There are other preventive measures too, but here is some backup code that you can run every morning if you care to:

http://www.ajenterprisesonline.com/_...BackupSource()

[Pilotwings_64]

Thanks for the reply.

So what if I have 10,000+ records and I find that one of them is corrupted? How do I proceed from there? I certainly couldn't check every single record in every single table to find out which ones were corrupted. Even if I could find out, how would I replace those corrupted records with good records?

[ajetrumpet]

you are asking a question that is not asked very often. Not a lot of people know the actual causes of corruption, nor do they know WHAT exactly gets corrupted inside the database. I am also in this group.

I don't have the answer. Thus, the reason for giving you a preventive solution. EG - backup your database and if you run into corruption issues, restore one of the previous versions you have. And yes, you'll have to reenter or re-modify data for the current day, but that's a heck of a lot better than re-creating your entire program, right?


I also don't know the best methods for testing corruption. I was thinking that Allen Browne might, but I don't remember ever reading a page on his website about this. I would guess though, that if actual records could get corrupted, they would throw errors if they were manipulated through a recordset in VBA. I really have no idea, but that makes sense to me. For instance, if you had an AutoExec macro that looped all of your tables from top to bottom and printed some field information out to the immediate window everytime the database was opened, I would assume that the program would throw an error after either entering the record position or before the print command if it was actually corrupt.

And something else too: I don't know the levels of corruption in detail, but I've never heard anyone ever talk about actual 'records' getting corrupted. Usually its the entire file, a module or another entity at the object-level in Access. If you think about it, how would you know exactly what record has been corrupted? And why would you simply want to replace it with a non-corrupted one?

To me, that would really be a waste of time because the risk of a table or even more info in the entire file could be corrupted. For instance, if too many created recordset objects in VBA (without being destroyed) could cause corruption, would you just write a new procedure or import a new module into the db if you found out that particular procedure was corrupt? NO. Because the code was obviously in contact with other objects in the database, so what's to say that they haven't been corrupted as well? Thus, eliminate every risk possible by restoring a complete file.

Make sense?

[Pilotwings_64]

Yes. It makes sense. I was just concerned that my database would get corrupted without my knowing, and I would go on using it for days, weeks, or months. Then the corruption would get bad enough to be noticed. In that case, using the last "good" file would mean giving up a lot of records. From what I understand of what you are saying, an Access database will show signs of corruption pretty much immediately. Is that true?

Thanks again for the help. I'm starting to see the issue a little more clearly.

[ajetrumpet]

an Access database will show signs of corruption pretty much immediately. Is that true?.

NO. Like I said before, corruption take place on any level. 'Level' means in a module, a record, form, report, database, a SINGLE BYTE of data in a field, etc...

Could be anything! You are never guaranteed to find it. You'll find it when you engage in a situation with the object or part of the file that is corrupt. You are looking for a failsafe here Pilot, so you don't ever run into a situation where your time is wasted and you have to backtrack. There are none.

That's impossible in this kind of work. It's a fact of life that we live with it.

[Pilotwings_64]

Okay, Thank you for your help.

[NTC]

Corruption at the data level (as opposed to the form or report level) is minimal, such that I have never seen it occur.

Disk drives are a greater probability of failure.

Presuming one does a properly scheduled backup, it is not an issue. Certainly it is no more an issue with Access than any other application or db.

[Pilotwings_64]

Thank you very much, NTC. I have never heard that said before.

[ajetrumpet]

Few Common causes for database corruption
Microsoft Office malfunction
Improper system shutdown while MS Access database is open
Operating system damage
Installing Service Packs
Third-party plug-ins
Network issues like broken cable connectors, switches, and network cards

To know more, read:
http://www.datarecovery-info.com/dat...-recovery.html

and while you are reading that article, consider buying products from them, as this hijack is obviously an indirect advertisement.

hey mods, if you are reading this, these types of things should be automatically junked. I would even go as far as to bet that forum trolling could be completely automated by now, as this last post would certainly indicate. May want to consider a tool to get rid of stuff like this?

[sampatrik]

Thanks for the reply.

So what if I have 10,000+ records and I find that one of them is corrupted? How do I proceed from there? I certainly couldn't check every single record in every single table to find out which ones were corrupted. Even if I could find out, how would I replace those corrupted records with good records?

I will suggest you that keep taking backup of your database at some interval of time so that if your database get corrupt then you can compare two databases and find out which record get corrupted or missing.

If your database get corrupted and you can't open your access database then you can use Stellar Phoenix Access Repair software to repair corrupted data.