What is a snapshot update conflict?

Under SNAPSHOT isolation, a transaction can read an older committed version without blocking a concurrent writer. However, if it later attempts to update a row that another transaction changed after the snapshot began, SQL Server may terminate the update with a snapshot update conflict.

The application must handle the error appropriately, often by reloading current data and retrying the complete transaction when the operation is safe to retry.

Row versioning reduces read blocking; it does not eliminate write-write conflicts.