btrebuild is an unsupported utility to re-create btree indexes.

ELOQUENCE BTREBUILD (C) Copyright 2013 Marxmeier Software AG (B.08.20)
usage: btrebuild [options] database [set[.index] ...]
options:
 -help   - show usage (this list)
 -u user - set user name
 -p pswd - set password
 -c cfg  - server configuration file
 -b size - Buffer cache size (MB), default 64
 -v      - verbose output
 -r      - readonly mode (testing)
 -m size - memory limit (MB), default 100
 -M      - use master key

A list of indexes may be specfied as argument: A set name or number
rebuilds all indexes for a set. A set name and exclamation mark (set.!)
rebuilds the primary index. A set name and index item name rebuilds
the specified index.
The btrebuild utility directly accesses the volume files and invalidates
replication or forward recovery. Make sure you have a valid backup.