Join indexes can be compressed at the data block level or not, depending on whether they have been compressed or decompressed using the Ferret utility. For information about the Ferret utility, see Utilities.
All limits on data block sizes apply to the noncompressed size of a join index. Block compression does not raise any of these limits, nor does it enable more data to be stored in a single data block than can be stored in an noncompressed data block of the same size.