A computer system employs file system software to maintain a transaction file that includes a plurality of transaction records that each include a header section and a data section. The file system software executes a startup process in which a reconstructed file system is generated in a random access memory. During startup, the file system software selectively verifies only the header section of a transaction record or both the header section and data section of a transaction record based on certain criterion. The transaction records may be stored in Flash memory.