When Helix can’t open a collection for some reason, the error dialog includes a number that indicates what sort of problem was found. Unfortunately, Helix 7.0.1 and earlier report most errors as ‘error 4’ (‘invalid contents’) which is rather a generic error.

Helix 7.0.2 and later return the unfiltered error code, making initial diagnosis of the actual problem easier.

For any of these errors, the best course of action is to revert to a previous verified backup. Consult the Repair Options for Collections that Report Unfixable Errors technote if you need to have the damaged copy repaired.

The chart below documents the errors that can be returned during the collection opening phase.