Microsoft KB Archive/98743

= ERR: &quot;Not a Database File&quot;; How to Modify Database Header =

Article ID: 98743

Article Last Modified on 12/3/2003

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APPLIES TO


 * Microsoft Visual FoxPro 3.0 Standard Edition
 * Microsoft Visual FoxPro 5.0 Standard Edition
 * Microsoft FoxPro 2.6 Standard Edition
 * Microsoft FoxPro 2.0
 * Microsoft FoxPro 2.6 for MS-DOS

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This article was previously published under Q98743





SUMMARY
When FoxPro returns the error message &quot;Not a Database File,&quot; you can sometimes correct the damaged file's header by using a hexadecimal file editor.

WARNING: Before attempting to modify a database in this way, it is STRONGLY recommended that you back up the database.

The structure of the database file header is given below.



MORE INFORMATION
The &quot;Not a database file&quot; error message in FoxPro 2.x may be caused by a record count value in the table header that is greater than the actual number of records. The Hexedit.app, distributed with Visual FoxPro 5.0 may be used in an attempt to correct the record count. In the Hexedit.app, a hexadecimal representation of the record count may be found at Address: 0000000 in columns 4, 5, 6, and 7. Use the calculator in Windows 95 or Windows NT to convert from decimal to hexadecimal and remember to reverse the order of the numbers as per this article.

For information about performing table maintenance using FoxPro low-level file functions, please see the following article in the Microsoft Knowledge Base:

135905 How to Retrieve Records that were Previously Zapped



WARNING: ANY USE BY YOU OF THE INFORMATION PROVIDED IN THIS ARTICLE IS AT YOUR OWN RISK. Microsoft provides this information &quot;as is&quot; without warranty of any kind, either expressed or implied, including but not limited to the implied warranties of merchantability and/or fitness for a particular purpose.



The table below identifies the bytes in the first part of the header:   Byte number   Description -

1            File-type identifier: 03 - DBF without memo (FoxBASE+/FoxPro/dBASE                        III PLUS/dBASE IV) 83 - DBF with memo (FoxBASE+/dBASE III PLUS) 8B - dBASE III with memo F5 - FoxPro with memo 2-4          Date of last update (YYMMDD) 5-8          Number of records in file* 9-10         Offset to start of data** 11-12        Size of record*** 13-28        Not used 29           Flag for compound index**** 30-32        Not used

* The number of records in the database is stored in reverse format. In other words, if those bytes were equivalent to F4 01 00 00, there would be 500 records in the database. 1F4h is the hexadecimal equivalent of decimal 500.

** The offset to the start of the data is computed from the beginning of the file to the first data record. It also is stored in reverse format. For example, if bytes 9 and 10 are 41 02, the first data record would begin at 241h, or 577 decimal bytes from the beginning of the file.

*** The size of the record also is stored in reverse format; the number represents the sum of the field sizes plus 1 because of    the deletion flag.

structural .CDX file attached to the database, and 00h if there is not an associated structural .CDX file. The second part of the header depends on the number of fields in the database. Each field uses 32 bytes. There is also a single terminating byte (0Dh) at the very end.
 * The flag for the compound index will be 01h if there is a

The field definition is as follows:   Byte number   Description --

1-11         Field name 12           Field type Character 43h Date     44h Logical  4Ch Memo     4Dh Numeric  4Eh 13-14        Offset of field from beginning of record 15-16        Not used 17-18        Field length (nonnumeric fields) 17           Field length (numeric fields) 18           Field decimals (numeric fields) 19-32        Not used FoxPro limits field names to ten characters; thus the eleventh byte, or the last (rightmost) byte, after the field name, must be null (00h). The field length is dependent upon the data type. Character fields use the seventeenth and eighteenth bytes, in reverse format.

Memo, date, and logical fields, which have fixed lengths of 10, 8, and 1, respectively, need only the first byte (17). The remaining bytes are generally nulls. However, keep in mind that there is a terminating byte of 0Dh at the very end of the header.

After the terminating 0Dh byte, the actual database data begins. The first byte of each record is the deletion flag. If the record has been deleted, but not packed, this byte will be 2Ah (an ASCII asterisk); otherwise, it is 20h (an ASCII space).

For DBF files created in Visual FoxPro for Windows, or 2.x DBF files added to a Database Container (DBC), the backlink information is stored between byte 0DH and the beginning of the data.

