Data Damage means your company file cannot be read correctly by QuickBooks. It may be caused by internal (within QuickBooks) or external (file location) factors. Majority of data damage issues can be repaired within QuickBooks.
This article lists top data damage errors you may encounter when using QuickBooks, including the ones that show as LVL errors in the QBWin.log.
There are different types of Data Damage
List Damage - lists (Chart of Accounts, Items, Customers, Suppliers, Employees, etc.).
Transaction Damage - one or more transactions.
Link Damage - links between transactions or the transactions themselves. Note: This type of damage can be challenging to determine. You may need to open the transaction to see where it is broken. Reports that do not match may also be caused by a damaged link.
Structural Damage - table/s or the header of the table.
Here is a list of top data damage errors in QuickBooks, with their corresponding data damage type and the transactions or modules affected: