The file could be damaged.
The file could have been improperly closed--such as would happen with a crash or a force quit.
The file could have been copied by the OS or a backup utility while open. (The copy, not the original will then require a consistency check...)
When a file is correctly closed, a flag on the file is set to show that it was properly closed. When the file is re-opened, FileMaker checks to see if this flag was set. If not, it runs a consistency check.
If you are closing the file with close file, quit aplication or by clicking the close button and the file has not been improperly closed or copied, you shouldn't get a consistency check. If this is the case, you need to run a recover on your file and test the recovered copy to see if the copy undergoes an automatic consistency check when opened.
Things to keep in mind about Recover:
While Recover almost always detects and fully corrects any problems with your file...
- The recovered copy may behave differently even if recover reports "no problems found".
- Recover does not detect all problems
- Recover doesn't always fix all problems correctly
- Best Practice is to never put a recovered copy back into regular use or development. Instead, replace the damaged file with an undamaged back up copy if this is at all possible. You may have to save a clone of the back up copy and import all data from your recovered copy to get a working copy with the most up to date information possible.