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dBase IV limitations
Last updated: 15 Nov 2003 by XpertSS.com
Approach can use a number of different database file structures, but uses dBaseIV by default. dBaseIV has the following limitations that you might need to be aware of:
- maximum file size = 2 gigabytes (per type .dbf or .dbt file)
- maximum records per database = 1,000,000,000 (1 billion)
- maximum of 30 open dBaseIV databases on a single computer
- maximum number of fields per record = 255
- maximum size of a record = 4000 characters (= all the field-lengths added together)
- Text field size equals the size defined in characters
- Date field uses 8 characters stored as text YYYYMMDD
- Time field uses 8 characters stored as text HHMMSSHH
- Boolean field uses 1 character (T, F or blank is stored)
- Memo or PicturePlus field uses 10 characters stored as a "record number" in the .DBT file
- Numeric field uses characters equal to the size definition plus 1. (Numeric 10.2 stores in 13 characters, 5.3 stores in 9 characters.
Some common error messages when using dBaseIV files:
- maximum length of a text field = 254 characters
- maximum number of characters in a dBaseIV memo field is 30,000 characters in releases prior to V9.8, which was fixed in that release to allow up to 65,536 (64KB).
Information about field names:
- -1003 when adding a field makes the record too long
- -1035 when the .DBT file has reached the 2 gigabyte limit and no more records can be added
Approach Field Definition allows up to 32 characters for field names, and it allows alphabetic letters, whole numbers, spaces, commas, periods, and arithmetic signs. If you delete the SmartIndex file (.ADX):
- Your field names are truncated to the dBaseIV standard of 10 characters, all capitals, with no blanks or special characters other than the underscore.
- Non-allowed characters and blanks will be replaced with the underscore.
- A "Time" field name will always end with the characters "TM9" so that Approach will know it is a time field.
- PicturePlus field names always end with the characters "PC9" so that Approach will know it is a PicturePlus field.
- dBaseIV Field names must be unique, so if you have field names that are the same in the first 10 characters, you will see a series of similar field names which may be difficult to work with. For example, "Customer Name", "Customer Number", "Customer Notice" will become "CUSTOMER_N", "CUSTOMER_2" and "CUSTOMER_3".
Information about sharing dBaseIV files:
Approach does not create or maintain the native dBaseIV index file for a database. This is important if you plan to also use the database in an application that depends on the presence of this index. Approach PicturePlus fields cannot be viewed in other dBASE applications.