Database Performance Document
... naive tuner might react to a high value in one of these measurements (e.g., high disk activity) by buying hardware to lower it (e.g., buy more disks). There are many cases, however, in which that would be inappropriate. For example, there may be high disk activity because some frequent query scans a ...
... naive tuner might react to a high value in one of these measurements (e.g., high disk activity) by buying hardware to lower it (e.g., buy more disks). There are many cases, however, in which that would be inappropriate. For example, there may be high disk activity because some frequent query scans a ...
Transaction
... Consistency means that The database is in a legal state when the transaction begins and ...
... Consistency means that The database is in a legal state when the transaction begins and ...
1. Introduction to Database
... does not lose data, controlled concurrency • High Throughput: many users => many transactions/sec • Low Response Time: on-line => users are waiting ...
... does not lose data, controlled concurrency • High Throughput: many users => many transactions/sec • Low Response Time: on-line => users are waiting ...
Functions of a DBMS
... CREATE TABLE … or ALTER TABLE … ADD CHECK(condition) PRIMARY KEY attribute-name FOREIGN KEY attribute-name REFERENCES parent-table The parent table must already have a primary key defined ...
... CREATE TABLE … or ALTER TABLE … ADD CHECK(condition) PRIMARY KEY attribute-name FOREIGN KEY attribute-name REFERENCES parent-table The parent table must already have a primary key defined ...
Chapter 10
... 10.2 Concurrency Control • Coordination of simultaneous transaction execution in a multiprocessing database • Objective is to ensure serializability of transactions in a multiuser environment • Simultaneous execution of transactions over a shared database can create several data integrity and consi ...
... 10.2 Concurrency Control • Coordination of simultaneous transaction execution in a multiprocessing database • Objective is to ensure serializability of transactions in a multiuser environment • Simultaneous execution of transactions over a shared database can create several data integrity and consi ...
Query Processing - Department of Computer Science
... several agents may be selling tickets, and therefore, changing lists of passengers and counts of available seats. The problem here is that if we are not careful when we allow two or more processes to access the database, we could sell the same seat twice. Here 2 processes that read and change the va ...
... several agents may be selling tickets, and therefore, changing lists of passengers and counts of available seats. The problem here is that if we are not careful when we allow two or more processes to access the database, we could sell the same seat twice. Here 2 processes that read and change the va ...
COMMIT - Telkom University
... Lost updates occur when two or more transactions selects the same row and then update the row based on the value originally selected. Each transactions is unaware of other transactions. The last update overwrites updates made by the other transactions, which results in lost data. A's update of 300 v ...
... Lost updates occur when two or more transactions selects the same row and then update the row based on the value originally selected. Each transactions is unaware of other transactions. The last update overwrites updates made by the other transactions, which results in lost data. A's update of 300 v ...
Two Phase Locking - Department of Computer Science
... • The part of the DBMS that keeps track of the locks issued to transactions is call the lock manager. The lock manager maintains a lock table which is a hash table with data object identifier as the key. The DBMS also maintains a descriptive entry for each transaction in a transaction table. The ent ...
... • The part of the DBMS that keeps track of the locks issued to transactions is call the lock manager. The lock manager maintains a lock table which is a hash table with data object identifier as the key. The DBMS also maintains a descriptive entry for each transaction in a transaction table. The ent ...
Chapter 7: Relational Database Design
... Schedule 3 below can be transformed into Schedule 1, a ...
... Schedule 3 below can be transformed into Schedule 1, a ...
marked
... View Serializability Let S and S´ be two schedules with the same set of transactions. S and S´ are view equivalent if the following three conditions are met: 1. For each data item Q, if transaction Ti reads the initial value of Q in schedule S, then transaction Ti must, in schedule S´, also read ...
... View Serializability Let S and S´ be two schedules with the same set of transactions. S and S´ are view equivalent if the following three conditions are met: 1. For each data item Q, if transaction Ti reads the initial value of Q in schedule S, then transaction Ti must, in schedule S´, also read ...
Distributed DBMS Advanced Topics
... global-abort message. Protocol assumes each site has its own local log and can rollback or commit transaction reliably. If participant fails to vote, abort is assumed. If participant gets no vote instruction from coordinator, can abort. ...
... global-abort message. Protocol assumes each site has its own local log and can rollback or commit transaction reliably. If participant fails to vote, abort is assumed. If participant gets no vote instruction from coordinator, can abort. ...
Text 13 Database Management Systems
... The greatest power of a DBMS, however, comes from its ability to quickly find and bring together information stored in separate tables using queries, forms, and reports. A query is a question or a request for specific data contained in a database. Database forms look similar to traditional printed f ...
... The greatest power of a DBMS, however, comes from its ability to quickly find and bring together information stored in separate tables using queries, forms, and reports. A query is a question or a request for specific data contained in a database. Database forms look similar to traditional printed f ...
Distributed Databases
... Only the data and software that exist at the failed site cannot be accessed. Replicating data and software at more than one site provides further improvement. If the data in the failed site had been replicated at another site prior to the failure, then the user will not be affected at all. 3. ...
... Only the data and software that exist at the failed site cannot be accessed. Replicating data and software at more than one site provides further improvement. If the data in the failed site had been replicated at another site prior to the failure, then the user will not be affected at all. 3. ...
distributed database
... transaction must commit or none must commit, and this property must be guaranteed despite any combination of site and link failures. This guarantee is achieved using a commit protocol. ...
... transaction must commit or none must commit, and this property must be guaranteed despite any combination of site and link failures. This guarantee is achieved using a commit protocol. ...
슬라이드 1
... multiple processors and multiple disks connected by a fast interconnection network. A coarse-grain parallel machine A massively parallel or fine grain parallel machine ...
... multiple processors and multiple disks connected by a fast interconnection network. A coarse-grain parallel machine A massively parallel or fine grain parallel machine ...
Transactions
... For example, a serializability order for graph in (a) would be graph in (b) or graph in (c). ...
... For example, a serializability order for graph in (a) would be graph in (b) or graph in (c). ...
Database Recovery
... accept new transactions. The system is in a quiet state and the database and transaction logs are synchronized All transactions in progress are completed and journal files are brought up-to-date DBMS writes a special record (checkpoint record) to the log file: snapshot of the state of the database C ...
... accept new transactions. The system is in a quiet state and the database and transaction logs are synchronized All transactions in progress are completed and journal files are brought up-to-date DBMS writes a special record (checkpoint record) to the log file: snapshot of the state of the database C ...
Josyala - ODU Computer Science
... Overview Distributed Transaction - Transactions that span two or more databases. - Incorporates several distinct operations occurring on different systems into an atomic action that succeeds or fails completely. Transfer() Charge() ...
... Overview Distributed Transaction - Transactions that span two or more databases. - Incorporates several distinct operations occurring on different systems into an atomic action that succeeds or fails completely. Transfer() Charge() ...
Document
... How we are used to resolve the problems while working with pessimistic concurrency levels ...
... How we are used to resolve the problems while working with pessimistic concurrency levels ...
Document
... Type of operation being performed (update, delete, insert) Names of objects affected by transaction “Before” and “after” values for updated fields Pointers to previous and next transaction log entries for the same transaction ...
... Type of operation being performed (update, delete, insert) Names of objects affected by transaction “Before” and “after” values for updated fields Pointers to previous and next transaction log entries for the same transaction ...
Distributed Database System
... transaction) in a distributed manner. A distributed database (DDB) can be defined as ◦ A distributed database (DDB) is a collection of multiple logically related database distributed over a computer network, and a distributed database management system as a software system that manages a distributed ...
... transaction) in a distributed manner. A distributed database (DDB) can be defined as ◦ A distributed database (DDB) is a collection of multiple logically related database distributed over a computer network, and a distributed database management system as a software system that manages a distributed ...
Access methods for time
... Transaction Range-Timeslice To answer a range query efficiently, it is best to cluster by transaction time and key within ...
... Transaction Range-Timeslice To answer a range query efficiently, it is best to cluster by transaction time and key within ...
Transactions - Dr Gordon Russell
... The goal in a ‘concurrent’ DBMS is to allow multiple users to access the database simultaneously without interfering with each other. A problem with multiple users using the DBMS is that it may be possible for two users to try and change data in the database simultaneously. If this type of action is ...
... The goal in a ‘concurrent’ DBMS is to allow multiple users to access the database simultaneously without interfering with each other. A problem with multiple users using the DBMS is that it may be possible for two users to try and change data in the database simultaneously. If this type of action is ...