| isfd | isam file identifier |
| key | description of index to cluster on or NULL |
SUCCESS, or a negative value on error, in which case the error code is found in iserrno.
the file must be open in exclusive mode
if key is NULL then the current index is used.
this routine makes use of a temporary file, created in the same directory as the original.
all active data records will be transferred to the temp file in the index order specified, and all indexes will be packed as efficiently as possible.
if successful, iscluster will return a new file descriptor, opened in the same format as the original, which will be erased.
a NULL pointer will be returned on error, and the original descriptor and file will be left intact.
be warned that this call may take some time to run if the file in question is large.