An append error can leave you uncertain whether the destination contains the intended import. Before pressing Run again, preserve the source, the message and the expected source record identifiers. A second attempt without that inventory can make reconciliation harder.

Inspect the destination in a database copy or through an authorised read-only query. Determine which expected identities are already present, which are absent and whether any present values differ from the source. Do not assume the message proves that either every row or no row was added.

Follow the reported failure category

Microsoft identifies four common causes. Type conversion failures mean a source value does not fit its target type. Key violations can breach a primary key or a no-duplicates index. Validation failures can involve required data, disallowed zero-length text or another rule. Lock violations can occur when the destination is open in Design View or affected by another user's access.

Compare the query's field mapping with the destination table design. If a numeric quantity column receives a descriptive label, fix the mapping instead of changing every rejected label into zero. If an identifier already exists, decide whether the source is a repeat, a correction or a genuinely new record.

Keep accepted and rejected identities visible

Build a reconciliation note with the intended record count and the identified outcomes. Include at least one example for each failure category reported. Counts help detect omissions, but matching identifiers and values establishes what the destination actually contains.

Do not remove a uniqueness or validation rule simply to make the error disappear. Confirm the data model and correct the source or mapping when the rule is doing its intended job. If the rule itself is outdated, handle that as a reviewed schema change.

For a lock problem, coordinate the access window with the database owner rather than forcing another user's session closed. Recheck the destination immediately before an approved retry, using a backed-up, tested process that accounts for records already present.

Finish by comparing the complete intended import with the destination again. Retain the original rejected values and their resolutions so a later audit can explain the difference between a missing record and a deliberately excluded one.

Sources: Microsoft: common Access append errors.