Indexed File Size Limits
The following file size limits affect indexed files:
- On Windows, the default (where IDXFORMAT=0) is IDXFORMAT 3.
- On UNIX, the default is IDXFORMAT 1 (C-ISAM) for fixed record length files and IDXFORMAT 3 for variable record length files.
To create files of a different format, use the IDXFORMAT extfh.cfg or compiler directive setting. To convert existing files to other formats, use the Rebuild utility.
| IDXFORMAT | Exclusive (#) | Exclusive with duplicate key compression on | Shared with default locking | FILEMAXSIZE set to |
|---|---|---|---|---|
| 1 | 4 Gb | 2 Gb | 1 Gb | 4 or 8 |
| 2 | 4 Gb | 2 Gb | 1 Gb | 4 or 8 |
| 3 | 4 Gb | 2 Gb | 1 Gb | 4 or 8 |
| 4 | 4 Gb | 2 Gb | 1 Gb | 4 or 8 |
| 8 | 4 Gb | 2 Gb | 1 Gb | 4 |
| 8 | 256 Tb | 128 Tb | 256 Tb | 8 |
where:
- (#) = either accessing files exclusively or accessing shared files with the extfh.cfg or compiler directive setting of LOCKTYPE 1 or 2. That is, file size is not affected when using LOCKTYPE 1 or 2.
- FILEMAXSIZE is an extfh.cfg setting that defaults to 4
- For IDXFORMAT 8 files only, if you increase the extfh.cfg setting
FILEPOINTERSIZE to 8, you increase file size limits to:
IDXFORMAT Exclusive (#) Exclusive with duplicate key compression on Shared with default locking FILEMAXSIZE set to 8 16 Eb 8 Eb 4 Eb 8
Notes:
- The above figures are determined by the pointer size used to address
the file. For example:
32 bits = 2^32 = 4,294,967,296 bytes = 4 Gb (Gigabytes) 48 bits = 2^48 = 281,474,976,710,656 bytes = 256 Tb (Terabytes) 64 bits = 2^64 = 18,446,744,073,709,551,616 bytes = 16 Eb (Exabytes or MegaTerabytes) - LOCKTYPE settings of 1 and 2 were specifically introduced in order to avoid the file size limit imposed by sharing files.
- If you set FILEMAXSIZE to 8, IDXFORMAT 8 supports very large files with the default locking mechanism. Therefore, you are recommended to use IDXFORMAT 8 for large files rather than any of the other formats which also require LOCKTYPE 1 or 2 for large files. (LOCKTYPE=1 has the disadvantage of not allowing locked data to be read at all while LOCKTYPE=2 has the disadvantage of using up an extra file handle for the .LCK file that contains the locks).
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