nKeep
multiple versions of a slowly changing state
oBe lazy about allocating space for a new version
▬Do it only when there’s new data in either
version
▬Otherwise, share the old data
oUsually in a database or file system
nThe
bet: Data won’t be overwritten.
oUsually an easy win.
nBig
win in latency when making a new version
nBig
win in bandwidth if versions differ little
nRep:
Data shared among versions (need GC)