Data Mgmt Lab_Part_58 - 172 1 2 3 4 Chapter 17 Serializable...

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172 Chapter 17 Serializable Conflict-serializable Recoverable Avoid cascading aborts 1 No No No No 2 No No Yes Yes 3 Yes Yes Yes Yes 4 Yes Yes Yes Yes Table 17.2 6. Multiversion concurrency control. Answer 17.4 Answer omitted. Exercise 17.5 For each of the following locking protocols, assuming that every trans- action follows that locking protocol, state which of these desirable properties are ensured: serializability, conflict-serializability, recoverability, avoidance of cascading aborts. 1. Always obtain an exclusive lock before writing; hold exclusive locks until end-of- transaction. No shared locks are ever obtained. 2. In addition to (1), obtain a shared lock before reading; shared locks can be released at any time. 3. As in (2), and in addition, locking is two-phase. 4. As in (2), and in addition, all locks held until end-of-transaction. Answer 17.5 See the table 17.2. Exercise 17.6 The Venn diagram (from [76]) in Figure 17.1 shows the inclusions between several classes of schedules. Give one example schedule for each of the regions
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This note was uploaded on 01/17/2012 for the course EGN 4302 taught by Professor Dr.vishak during the Fall '12 term at University of Central Florida.

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Data Mgmt Lab_Part_58 - 172 1 2 3 4 Chapter 17 Serializable...

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