WGU C170 Chapter 5 Complete

WGU C170 Chapter 5 Complete access plan Ans- A set of instructions generated at application compilation time that is created and managed by a DBMS. The access plan predetermines how an application's query will access the database at run time. algorithms Ans- A process or set of operations in a calculation. automatic query optimization Ans- A method by which a DBMS finds the most efficient access path for the execution of a query. B-tree index Ans- An ordered data structure organized as an upside-down tree. bitmap index Ans- An index that uses a bit array (0s and 1s) to represent the existence of a value or condition. buffer cache Ans- See data cache data cache Ans- A shared, reserved memory area that stores the most recently accessed data blocks in RAM. Also called buffer cache. data files Ans- A named physical storage space that stores a database's data. It can reside in a different directory on a hard disk or on one or more hard disks. All data in a database is stored in data files. A typical enterprise database is normally composed of several data files. A data file can contain rows from one or more tables. data sparsity Ans- A column distribution of values or the number of different values a column can have. database performance tuning Ans- A set of activities and procedures designed to reduce the response time of a database system—that is, to ensure that an end-user query is processed by the DBMS in the minimum amount of time. database statistics Ans- In query optimization, measurements about database objects, such as the number of rows in a table, number of disk blocks used, maximum and average row length, number of columns in each row, and number of distinct values in each column. Such statistics provide a snapshot of database characteristics. DBMS performance tuning Ans- Activities to ensure that clients' requests are addressed as quickly as possible while making optimum use of existing resources. dynamic query optimization Ans- The process of determining the SQL access strategy at run time, using the most up-to-date information about the database extents Ans- In a DBMS environment, refers to the ability of data files to expand in size automatically using predefined increments. file group Ans- See table space. hash index Ans- An index based on an ordered list of hash values. input/output (I/O) request Ans- A low-level data access operation that reads or writes data to and from computer devices. manual query optimization Ans- An operation mode that requires the end user or programmer to define the access path for the execution of a query. manual statistical generation mode Ans- A mode of generating statistical data access information for query optimization. In this mode, the DBA must periodically run a routine to generate the data access statistics—for example, running the RUNSTAT command in an IBM DB2 da