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.
...
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 database.
procedure cache Ans- See SQL cache.
query optimizer Ans- A DBMS process that analyzes SQL queries and finds the most efficient way to
access the data. The query optimizer generates the access or execution plan for the query.
query processing bottleneck Ans- In query optimization, a delay introduced in the processing of an I/O
operation that causes the overall system to slow down.
rule-based query optimization algorithm Ans- A query optimization technique that uses preset rules and
points to determine the best approach to executing a query.
SQL cache Ans- A shared, reserved memory area that stores the most recently executed SQL statements
or PL/SQL procedures, including triggers and functions. Also called procedure cache.
SQL performance tuning Ans- Activities to help generate a SQL query that returns the correct answer in
the least amount of time, using the minimum amount of resources at the server end.
static query optimization Ans- A query optimization mode in which the access path to a database is
predetermined at compilation time.
statistically based query optimization algorithm Ans- A query optimization technique that uses statistical
information about a database. The DBMS then uses these statistics to determine the best access
strategy.
table space Ans- In a DBMS, a logical storage space used to group related data. Also known as a file
group
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