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INTRO. TO DATABASE MGMT. SYST.
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Validation‐based concurrency control always requires buffering all writes until commit time.
Which of the following scheduling graphs indicates a cycle (and thus non‐serializable schedule)?
Consider two transactions T1 and T2 with timestamps TS(T1)=5 and TS(T2)=10 and the following schedule:
T1. | T2--------------+------------- write(A) | | read(A)
Under the basic timestamp ordering protocol, what happens?
Consider the following transaction schedule. Indicate if it is conflict-serializable or not:
| T1 | T2+---------+--------| read(A) | | | read(B)| read(B). | | | write(B)| write(A) | | write(B) | | | read(A)| | write(A)| commit | | | commit
Consider this schedule under basic 2PL where locks may be released as soon as the write is done (so uncommitted writes can be seen by others)
| T1 | T2+--------------+-------------| lock_X(A) | | write(A) | | unlock(A) | | | lock_S(A)| | read(A)| abort | | |
Under this protocol, does the schedule exhibit
Under basic two‐phase locking, once a transaction releases any lock, it cannot acquire any new locks.
Deadlock avoidance using wait‐die and wound‐wait schemes is typically integrated with which protocol?
In a timestamp‐ordering protocol, a read operation may ever cause the reading transaction to abort if the data item was last written by a younger transaction.
Consider the following schedule under basic 2PL
| T1 | T2+--------------+-------------| lock_S(A) | | | lock_S(B)| lock_X(B) | | | lock_X(A)
Under this 2PL protocol, does the schedule exhibit
Assuming that and are sets and and