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9 Cards in this Set

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  • Back
2PL
Two-Phase Lock
3 Types of Lock
Read Lock (Shared Lock)
Write Lock (Exclusive Lock)
Unlocked
deadlock detection
system keeps wait-for graph.when T is blocked by T' draw line from T to T'. A cycle implies deadlock.
No waiting
if T1 tries to lock(x), and xis locked in conflicting mode by T2, T1 is aborted
Cautious waiting
if T1 tries to lock(x), and xis locked in conflicting mode by T2, if T2 is blocked then abort T1 else T1 waits
Wound-Wait (preemptive)
if Ti requests an item held in a conflicting mode by another transaction Tj. if Ti < Tj, then abort Tj, else Ti waits. Waits on older transaction.
Wait-Die (non-preemptive)
if Ti requests an item held in a conflicting mode by another transaction Tj. if Ti < Tj, Then Ti waits. else abort Ti. Waits on younger transaction.
timestamp ordering
only allows one equivalent serial schedule
multiversion TO
read operations are always successful