Database corruption overview
* Backup files not recognizable by database engine
* Database locked as ‘suspect’ preventing access
* Deleted or dropped tables
* Accidentally deleted records
* Corrupted database files and devices
* Damaged individual data pages
* Accidentally overwritten database files & devices
A corrupt database will usually (but not always) show symptoms—sometimes extreme symptoms such as one or more of the following:
• Database can’t be browsed, causing a system error
• Not all records can be retrieved
• Unable to perform various tasks such as Recover Database or Copy Database
• Hugely overblown database file size
Intermediate symptoms like these might appear:
• Uncertainty over just how many records in the database
• Error messages when creating new reports, for example
• Thrown back to Main menu and password cleared when attempting, for example, to access the Program Spec or Restrict Spec
“Mild” symptoms like the following might appear:
• Report doesn’t print—No records found message
• Spurious characters in data fields or Retrieve Specs
• Database file inexplicably omitted from backup
A database can show no symptoms at all and still be corrupted.
Ironically, the most dramatic symptoms can be the result of minor damage and the most innocuous symptoms can be evidence of irreparable corruption. A database that can’t even be browsed might be fully repaired by recovering it. On the other hand, a very severely damaged database might show no ill effects whatever during day to day use, but be damaged beyond recovery, copying, or modification.
What can you do about corruption?
Rule No. 1 when you suspect you have a damaged database is:
Set aside any old backups of the database—DO NOT overwrite them. Then, make a new backup of the database and put it in a safe place.
This way you’re always working on a copy, or have backup copy available in case any of your actions further damage the database (which is quite likely).
It’s absolutely vital to frequently backup your databases. How frequent? Each day, or several times each day, you should backup all the data you can’t afford to lose or re-enter. What’s more, you should retain older backups (not just overwrite one backup with another) in case a database has gone bad over time without you noticing it. One day, all your attempts at data recovery might fail, in which case all you’ll have is your most recent viable backup. By viable I mean that which can be effectively restored. So you should perform test restores from time to time to ensure your backups are okay.
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