Special Considerations for Text Files

You can use the Microsoft Jet text IISAM driver to link and open character-delimited and fixed-length text files. Commas, tabs, or user-defined delimiters are valid in the source file.

Microsoft Jet recognizes Null values in character-delimited files by the presence of two consecutive delimiting characters. Microsoft Jet recognizes Null values in fixed-length files by the absence of data (spaces) in the data column.

Microsoft Jet determines the format of the text file by reading the file directly or by using a schema information file. The schema information file, which is always named Schema.ini and is always kept in the same location as the text data source, provides the IISAM driver with information about the general format of the file, the column name and data type information, and a number of other data characteristics. A Schema.ini file is always required for accessing fixed-length data; a Schema.ini file is recommended when your text table contains Date/Time, Currency, or Decimal data or any time you want more control over the handling of the data in the table.

Important Microsoft Jet doesn’t support multiuser access to text files. When you open a text file through Microsoft Jet, you have exclusive access to the file.

The following table lists the few limitations to the size of text tables and objects.