Let a database contain initial values x=3, y=6, z=9 Suppose the logging-and-recovery scheme uses deferred update, the log can contain only the after-image values, that is, log records for write_item operations have only a single value. The new value of database element written. let the log contain the sequence of records: [Checkpoint] [start_transaction, T1] [write_item, T1,x,6] [write_item, T1,y,9] [commit, T1] [start_transaction, T2] [write_item, T2,x,9] [start_transaction, T3] [write_item, T3,y,12] [write_item, T3,z,12] [commit, T3] [write_item, T2,y,3] Determine all the possible values of data items x, y, and z that might be written on disk during the execution of the above log operations. a) x=6, y=6, z=9 b) x=9, y=9, z=9 c) x=9, y=9, z=12 d) x=9, y=12, z=9
Let a database contain initial values x=3, y=6, z=9 Suppose the logging-and-recovery scheme uses deferred update, the log can contain only the after-image values, that is, log records for write_item operations have only a single value. The new value of database element written. let the log contain the sequence of records: [Checkpoint] [start_transaction, T1] [write_item, T1,x,6] [write_item, T1,y,9] [commit, T1] [start_transaction, T2] [write_item, T2,x,9] [start_transaction, T3] [write_item, T3,y,12] [write_item, T3,z,12] [commit, T3] [write_item, T2,y,3] Determine all the possible values of data items x, y, and z that might be written on disk during the execution of the above log operations. a) x=6, y=6, z=9 b) x=9, y=9, z=9 c) x=9, y=9, z=12 d) x=9, y=12, z=9
Computer Networking: A Top-Down Approach (7th Edition)
7th Edition
ISBN:9780133594140
Author:James Kurose, Keith Ross
Publisher:James Kurose, Keith Ross
Chapter1: Computer Networks And The Internet
Section: Chapter Questions
Problem R1RQ: What is the difference between a host and an end system? List several different types of end...
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| 5. | Let a [Checkpoint] [start_transaction, T1] [write_item, T1,x,6] [write_item, T1,y,9] [commit, T1] [start_transaction, T2] [write_item, T2,x,9] [start_transaction, T3] [write_item, T3,y,12] [write_item, T3,z,12] [commit, T3] [write_item, T2,y,3] Determine all the possible values of data items x, y, and z that might be written on disk during the execution of the above log operations. |
| a) | x=6, y=6, z=9 | ||
| b) | x=9, y=9, z=9 | ||
| c) | x=9, y=9, z=12 | ||
| d) | x=9, y=12, z=9 |
which one ?
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