SAP Note 26154 - Error with INSERT for file AUAK

Symptom:

Description: During the settlement, an update termination occurs with
the following error message.
Error message: KD533 'system error during INSERT for file AUAK (Return
code = 4)'
Program: LKO78U01, FUNCTION K_SETTLEMENT_DOCUMENT_INSERT

Cause and prerequisites

An attempt was made to update a settlement document with an existing document number. Presumably, a mistake was made concerning the number assignment for the settlement document numbers.

Solution
With the help of the transaction KO8N (number ranges for settlement documents cost element itemizations; can be accessed by means of various Customizing menus as subfunction of the settlement Customizing), you can determine the number intervals and the current number level for settlement document numbers.
Please set the interval limits or the current number level so that no settlement document numbers exist yet between current number level and upper interval limit.
You can determine the existing document numbers with the help of the transaction SE16 (general table display) for the table AUAK.