This section is from the "Version Control with Subversion" book, by Ben Collins-Sussman, Brian W. Fitzpatrick and C. Michael Pilato. Also available from Amazon: Version Control with Subversion.
svnadmin deltify — Deltify changed paths in a revision range.
svnadmin deltify exists in current versions of Subversion only for historical reasons. This command is deprecated and no longer needed.
It dates from a time when Subversion offered administrators greater control over compression strategies in the repository. This turned out to be a lot of complexity for very little gain, and this “feature” was deprecated.