quotalegacy?

[Shelley Waltz]

I have a cyrus-2.2.3 installation with quotas appearing as flat files
in /var/lib/imap/quota/(a-z)/user.*  Each file has 2 lines, the quota
and the current useage.  I process these files to generate quota warnings
for users in advance of reaching their limit.  In the imapd.conf(5) man
page for this distribution, there is no configuration choice for
quota_db .

In my new 2.3.7 RHAS5 distribution, quota_db choices are
quotalegacy(default),
flat,berkeley,berkeley-hash,skiplist.  What is quotalegacy - is it what I
have in my 2.2.3 distribution?  How is this different from flat?

confused,
S