Bugzilla optimizes database lookups by storing all relatively - static information in the - versioncache file, located in the - data/ - subdirectory under your installation directory.
If you make a change to the structural data in your database (the - versions table for example), or to the - "constants" - - encoded in defparams.pl, you will need to remove - the cached content from the data directory (by doing a - "rm data/versioncache" - - ), or your changes won't show up.
versioncache - gets automatically regenerated whenever it's more than - an hour old, so Bugzilla will eventually notice your changes by itself, - but generally you want it to notice right away, so that you can test - things.