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20 Cards in this Set
- Front
- Back
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Nine Functions of a DBMS
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1) Update and Retrieve Data
2) Provide catalog services 3) Support concurrent update 4) Recover data 5) Provide security services 6) Provide data integrity features 7) Support data independence 8) Support data replication 9) Provide utility services |
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What is metadata? What are some examples of metadata?
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metadata is data about the data in a database
It includes table descriptions and field definitions |
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What is a data dictionary?
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A data dictionary is a supercatalog storing more than described in the catalog. (for large DBMS)
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When does a concurrent update occur?
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A concurrent update occurs when multiple users make updates to the same database at the same time
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What is batch processing?
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A technique whereby all updates are stored in one file and executed at a specific time in a day all at once
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What is the biggest problem with batch updating?
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As soon as changes are made, the data is no longer current.
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How does locking solve the problem of concurrent updating?
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Locking denies access by other users to data while the DBMS processes one user's updates to the database.
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What is a transaction?
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A transaction is a set of actions that make up a single task to be completed.
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What is two-phase locking?
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The technique that states that the DBMS should hold locks until it completes all updates in a give transaction.
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What is the growing phase in two phase locking?
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The phase in which the DBMS locks more rows and releases none of the locks.
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What is the shrinking phase in two phase locking?
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The phase in which the DBMS releases all locks and acquires no new locks
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What is a deadlock (aka, deadly embrace)
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When two locks conflict, so as without any intervention, the conflict will never be resolved.
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Who is the victim in a deadlock?
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The person who's transaction gets denied
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What is timestamping?
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Timestamping is a system used by the database to prevent deadlocks by assigning each database update the unique time when the database updated.
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What is recovery?
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Recovery is the process of returning the database to a known-good state from a state known to be incorrect.
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What is journaling?
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Journaling involves maintaining a journal, or log, of all updates in a database for recovery purposes
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What are before and after images?
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They are records of a change before and after an update to a given row
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What is forward recovery?
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Process of recovering a database by using a database backup and applying all updates logged until the disaster
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What is backward recovery?
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Process of recovering a database by using the current database and rolling back updates until the database is restored
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What are the three types of data integrity?
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Data type integrity
Legal values integrity Format Integrity |
