if your program crashesyour changes are not retained unless you explicitly commit them to the database automatic updates for some types of in-memory object changes objects in zodb derived from persistence superclass are smart enough to know the database must be updated when an attribute is assigned automatic caching of objects objects are cached in memory for efficiency and are automatically removed from the cache when they haven' been used platform-independent storage because zodb stores your database in single flat file with large-file supportit is immune to the potential size constraints and dbm filesystem format differences of shelves as we saw earlier in this shelve created on windows using bsddb may not be accessible to script running with gdbm on linux because of such advantageszodb is probably worth your attention if you need to store python objects in database persistently in production environment the only significant price you'll pay for using zodb is small amount of extra codeaccessing the database requires small amount of extra boilerplate code to interface with zodb--it' not simple open call classes are derived from persistence superclass if you want them to take advantage of automatic updates on changes--persistent classes are generally not as completely independent of the database as in shelvesthough they can be considering the extra functionality zodb provides beyond shelvesthese trade-offs are usually more than justified for many applications the mostly missing zodb tutorial unfortunatelyas write this edition in june zodb is not yet available for python xthe version used in this book because of thatthe prior edition' python examples and material have been removed from this section howeverin deference to python usersas well as readers of some bright future where -base zodb has materializedi've made the prior edition' zodb materials and examples available in this edition' examples package see the preface for details on the examples packageand see these locations within it for more on zodbc:\dbase\zodb- :\dbase\zodb- \documentaion zodb examples code third edition the rd edition' zodb tutorial although cannot predict the futurezodb will likely become available for python eventually in the absence of thisother python-based oodbs may offer additional options databases and persistence