Database Transactions and Processess
... With this type of compensation, when a transaction aborts, the value of every item it changed is eventually restored to the value it had before that transaction started ...
... With this type of compensation, when a transaction aborts, the value of every item it changed is eventually restored to the value it had before that transaction started ...
Chapter 7: Relational Database Design
... A schedule is conflict serializable if and only if its precedence graph is acyclic. Cycle-detection algorithms exist which take order n2 time, where n is the number of vertices in the graph. (Better algorithms take order n + e where e is the number of edges.) If precedence graph is acyclic, th ...
... A schedule is conflict serializable if and only if its precedence graph is acyclic. Cycle-detection algorithms exist which take order n2 time, where n is the number of vertices in the graph. (Better algorithms take order n + e where e is the number of edges.) If precedence graph is acyclic, th ...
ppt
... The precedence graph test for conflict serializability cannot be used directly to test for view serializability. ...
... The precedence graph test for conflict serializability cannot be used directly to test for view serializability. ...
Document
... transaction has completed (i.e., the transfer of the $50 has taken place), the updates to the database by the transaction must persist despite failures. ...
... transaction has completed (i.e., the transfer of the $50 has taken place), the updates to the database by the transaction must persist despite failures. ...
Document
... 1. Read and execution phase: Transaction Ti writes only to temporary local variables 2. Validation phase: Transaction Ti performs a ``validation test'' to determine if local variables can be written without violating serializability. 3. Write phase: If Ti is validated, the updates are applied to the ...
... 1. Read and execution phase: Transaction Ti writes only to temporary local variables 2. Validation phase: Transaction Ti performs a ``validation test'' to determine if local variables can be written without violating serializability. 3. Write phase: If Ti is validated, the updates are applied to the ...
Document
... Distributed DBMS Architecture Distributed Database Design Semantic Data Control Distributed Query Processing Distributed Transaction Management ...
... Distributed DBMS Architecture Distributed Database Design Semantic Data Control Distributed Query Processing Distributed Transaction Management ...
Pangea: An Eager Database Replication Middleware
... • We propose a new correctness criterion for eager replicated database systems called global snapshot isolation (GSI). GSI not only guarantees SI to clients but also maintains consistency between database servers. • We propose a novel concurrency control which creates snapshots in a synchronized fas ...
... • We propose a new correctness criterion for eager replicated database systems called global snapshot isolation (GSI). GSI not only guarantees SI to clients but also maintains consistency between database servers. • We propose a novel concurrency control which creates snapshots in a synchronized fas ...
Document
... Every conflict serializable schedule is also view serializable. Schedule 9 (from text) — a schedule which is view-serializable but not conflict serializable. ...
... Every conflict serializable schedule is also view serializable. Schedule 9 (from text) — a schedule which is view-serializable but not conflict serializable. ...
ppt
... a single transaction failure leads to a series of transaction rollbacks. Consider the following schedule where none of the transactions has yet committed (so the schedule is recoverable) If T10 fails, T11 and T12 must also be rolled back. ...
... a single transaction failure leads to a series of transaction rollbacks. Consider the following schedule where none of the transactions has yet committed (so the schedule is recoverable) If T10 fails, T11 and T12 must also be rolled back. ...
Minimum Spanning Trees - Jordan University of Science and
... This specifies that read and write transaction operations have ended and marks the end limit of transaction execution. At this point it may be necessary to check whether the changes introduced by the transaction can be permanently applied to the database or whether the transaction has to be abor ...
... This specifies that read and write transaction operations have ended and marks the end limit of transaction execution. At this point it may be necessary to check whether the changes introduced by the transaction can be permanently applied to the database or whether the transaction has to be abor ...
ppt
... • Transactions that have written their commit entry in the log must also have recorded all their write operations in the log; otherwise they would not be committed, so their effect on the database can be redone from the log entries. (Notice that the log file must be kept on disk. • At the time of a ...
... • Transactions that have written their commit entry in the log must also have recorded all their write operations in the log; otherwise they would not be committed, so their effect on the database can be redone from the log entries. (Notice that the log file must be kept on disk. • At the time of a ...
Document
... The precedence graph test for conflict serializability must be modified to apply to a test for view serializability. The problem of checking if a schedule is view serializable falls in the class of NP-complete problems. Thus existence of an efficient algorithm is unlikely. However practical algori ...
... The precedence graph test for conflict serializability must be modified to apply to a test for view serializability. The problem of checking if a schedule is view serializable falls in the class of NP-complete problems. Thus existence of an efficient algorithm is unlikely. However practical algori ...
Chapter 14: Concurrency Control
... Given a transaction Ti that does not follow two-phase locking, we can find a transaction Tj that uses two-phase locking, and a schedule for Ti and Tj that is not conflict serializable. ...
... Given a transaction Ti that does not follow two-phase locking, we can find a transaction Tj that uses two-phase locking, and a schedule for Ti and Tj that is not conflict serializable. ...
Lock-Based Protocols
... Problems with SI SI does not always give serializable executions Serializable: among two concurrent txns, one sees the effects of the other In SI: neither sees the effects of the other Result: Integrity constraints can be violated ...
... Problems with SI SI does not always give serializable executions Serializable: among two concurrent txns, one sees the effects of the other In SI: neither sees the effects of the other Result: Integrity constraints can be violated ...
Document
... concurrency. Two-phase locking on an index may result in transactions executing practically one-at-a-time. It is acceptable to have nonserializable concurrent access to an index as long as the accuracy of the index is maintained. In particular, the exact values read in an internal node of a B+-tree ...
... concurrency. Two-phase locking on an index may result in transactions executing practically one-at-a-time. It is acceptable to have nonserializable concurrent access to an index as long as the accuracy of the index is maintained. In particular, the exact values read in an internal node of a B+-tree ...
Document
... The precedence graph test for conflict serializability must be modified to apply to a test for view serializability. The problem of checking if a schedule is view serializable falls in the class of NP-complete problems. Thus existence of an efficient algorithm is unlikely. However practical algori ...
... The precedence graph test for conflict serializability must be modified to apply to a test for view serializability. The problem of checking if a schedule is view serializable falls in the class of NP-complete problems. Thus existence of an efficient algorithm is unlikely. However practical algori ...
งานนำเสนอ PowerPoint
... Locking : A procedure used to control concurrent access to data. When one transaction is accessing the database, a lock may deny access to other transactions to prevent incorrect results. Locking methods are the most widely used approach to ensure serializability of concurrent transactions. There a ...
... Locking : A procedure used to control concurrent access to data. When one transaction is accessing the database, a lock may deny access to other transactions to prevent incorrect results. Locking methods are the most widely used approach to ensure serializability of concurrent transactions. There a ...
A Critical Comparison of NOSQL Databases in the Context of Acid
... use the BASE model because they do not usually comply with ACID model, something used by relational databases. However, some NOSQL databases adopt additional approaches and techniques to make the database comply with ACID model. In this light, this paper will explore some of these approaches and exp ...
... use the BASE model because they do not usually comply with ACID model, something used by relational databases. However, some NOSQL databases adopt additional approaches and techniques to make the database comply with ACID model. In this light, this paper will explore some of these approaches and exp ...
Document
... Thus, if we decide that a committed transaction was a mistake, then we must perform another transaction to reverse it. On the other hand, an aborted transaction can be restarted later, and depending on the cause of failure, may successfully execute and commit at that time. A DBMS has no way of ...
... Thus, if we decide that a committed transaction was a mistake, then we must perform another transaction to reverse it. On the other hand, an aborted transaction can be restarted later, and depending on the cause of failure, may successfully execute and commit at that time. A DBMS has no way of ...
Transactions
... previously written by Ti, the commit operation of Ti appears before the read operation of Tj. Every cascadeless schedule is also recoverable It is desirable to restrict the schedules to those that are cascadeless ...
... previously written by Ti, the commit operation of Ti appears before the read operation of Tj. Every cascadeless schedule is also recoverable It is desirable to restrict the schedules to those that are cascadeless ...
Chapter 20: Advanced Transaction Processing
... Main-Memory Database Optimizations To reduce space overheads, main-memory databases can ...
... Main-Memory Database Optimizations To reduce space overheads, main-memory databases can ...
Spring 2002 Transaction Information Systems
... View-Serializability • Let transaction T has k read steps. Let S be a schedule that includes transaction T. The view of T in S is a set of values that T read from database. • Two schedules S and S’ are view-equivalent if and only if they are final state equivalent and the view of each transaction i ...
... View-Serializability • Let transaction T has k read steps. Let S be a schedule that includes transaction T. The view of T in S is a set of values that T read from database. • Two schedules S and S’ are view-equivalent if and only if they are final state equivalent and the view of each transaction i ...
Chapter 7: Relational Database Design
... does not exist such a serial schedule, being eqvivalent (view or conflict) to the given one. The schedule is surely correct, if it is serializable How to check serializability? ...
... does not exist such a serial schedule, being eqvivalent (view or conflict) to the given one. The schedule is surely correct, if it is serializable How to check serializability? ...
Document
... has completed (i.e., the transfer of the $50 has taken place), the updates to the database by the transaction must persist even if there are software or hardware failures. ...
... has completed (i.e., the transfer of the $50 has taken place), the updates to the database by the transaction must persist even if there are software or hardware failures. ...
Why Transactions?
... Isolation Levels: In Summary (cont’d) REPEATABLE READS (Level 2) All reads are consistent for the life of a transaction Shared locks are NOT released after the data is processed Does not protect entire set (i.e. phantoms may occur) ...
... Isolation Levels: In Summary (cont’d) REPEATABLE READS (Level 2) All reads are consistent for the life of a transaction Shared locks are NOT released after the data is processed Does not protect entire set (i.e. phantoms may occur) ...