> ZODB defines these levels but I can not see any code in the ZODB package
> that actually uses these levels.
Nevertheless, grep'ing the ZODB source for TRACE and BLATHER will find them.
TRACE is used only in modules under ZEO/zrpc/, and gives extremely verbose
output about bare-metal ZEO communications. Only someone trying to debug
low-level ZEO socket or protocol problems would want to use TRACE.
For more information about ZODB, see the ZODB Wiki:
ZODB-Dev mailing list - ZODB-Dev@zope.org