Multi-version Concurrency Control (cont)
Advantage of MVCC
- locking needed for serializability considerably reduced
Disadvantages of MVCC
- visibility-check overhead (on every tuple read/write)
- reading an item V causes an update of RTS(V)
- storage overhead for extra versions of data items
- overhead in removing out-of-date versions of data items
Despite apparent disadvantages, MVCC is very effective.
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