[Zodb-checkins] CVS: ZODB3 - NEWS.txt:1.41

[Jeremy Hylton]

Update of /cvs-repository/ZODB3
In directory cvs.zope.org:/tmp/cvs-serv8546

Modified Files:
	NEWS.txt 
Log Message:
Add text about MVCC


=== ZODB3/NEWS.txt 1.40 => 1.41 ===
--- ZODB3/NEWS.txt:1.40	Mon Jan  5 15:46:18 2004
+++ ZODB3/NEWS.txt	Mon Jan  5 16:00:18 2004
@@ -1,4 +1,4 @@
-What's new in ZODB3 3.3 alpha 1
+What's new in ZODB3 3.3 alpha 2
 ===============================
 Release-date: XX-XXX-2003
 
@@ -24,8 +24,18 @@
 - persistent.mapping.PersistentMapping
 - persistent.TimeStamp
 
-ZODB now supports multi-version concurrency control for storages that
-support multiple revisions.  XXX
+ZODB now supports multi-version concurrency control (MVCC) for
+storages that support multiple revisions.  FileStorage and
+BDBFullStorage both support MVCC.  In short, MVCC means that read
+conflicts should almost never occur.  When an object is modified in
+one transaction, other concurrent transactions read old revisions of
+the object to preserve consistency.  In earlier versions of ZODB, any
+access of the modified object would raise a ReadConflictError.
+
+The ZODB internals changed significantly to accommodate MVCC.  There
+are relatively few user visible changes, aside from the lack of read
+conflicts.  It is possibe to disable the MVCC feature using the mvcc
+keyword argument to the DB open() method, ex.: db.open(mvcc=False).
 
 Changed the ZEO server and control process to work with a single
 configuration file; this is now the default way to configure these