some more findings: 1. The conflict error really happens on the Portalcatalog 2. It is a BTreesConflictError: BTrees conflict error at -1/47/47: Conflicting inserts which disguised as ConflictError, through the various try: excepts: 3. It happens on DateIndexes like "created" and "modified". 4. I put for a test: try: resolved = resolve(old, committed, newstate) except: return "invalidated" into tryToResolveConflict and into the store-method of FileStorage: if serial != cached_tid: rdata = self.tryToResolveConflict(oid, cached_tid,serial, data) if rdata is None: raise POSException.ConflictError(oid=oid, serials=(cached_tid, serial), data=data) elif rdata == "invalidated": #new for test old = False # pass # With these hacks I get rid of the conflictErrors. But when I delete the created Items I get: 2007-06-01 13:20:33 ERROR Zope.UnIndex DateIndex: unindex_object tried to retrieve set 1075379718 from index created but couldn't. This should not happen. 2007-06-01 13:20:33 ERROR Zope.UnIndex DateIndex: unindex_object tried to retrieve set 1075379838 from index Date but couldn't. This should not happen. 2007-06-01 13:20:33 ERROR Zope.UnIndex DateIndex: unindex_object tried to retrieve set 1075379719 from index modified but couldn't. This should not happen. So obviously I just fix the symptom with this hack. I think the real cause: lies in these lines: if old: cached_tid = self._get_cached_tid(oid) if cached_tid is None: h = self._read_data_header(old, oid) if h.version: if h.version != version: raise VersionLockError(oid, h.version) pnv = h.pnv cached_tid = h.tid if serial != cached_tid: rdata = self.tryToResolveConflict(oid, cached_tid,serial, data) Which is also supported by the fact, that on our live system which is running on 4 zeo-clients we get this traceback: 2007-06-01T12:38:59 ERROR Zope.SiteErrorLog http://uniben.waeup.org/campus/students/F541700/study_course/create_level Traceback (innermost last): Module Zope2.App.startup, line 173, in zpublisher_exception_hook Module ZPublisher.Publish, line 121, in publish Module Zope2.App.startup, line 240, in commit Module transaction._manager, line 96, in commit Module Products.CPSCompat.PatchZODBTransaction, line 175, in commit Module transaction._transaction, line 436, in _commitResources Module ZODB.Connection, line 665, in tpc_vote Module ZEO.ClientStorage, line 893, in tpc_vote Module ZEO.ClientStorage, line 877, in _check_serials ConflictError: database conflict error (oid 0x8fe833, class BTrees._IOBTree.IOBucket, serial this txn started with 0x036e0418ddcccf55 2007-06-01 11:36:51.984384, serial currently committed 0x036e041a3a33e311 2007-06-01 11:38:13.641254) Any suggestion for a temporary fix would be very welcome, since we get about 6000 conflict errors per day now about 15 % unresolved, and they are really killing our portal. -- Gruß Joachim