Database Reference
In-Depth Information
Cost based SQL optimizer (CBO)
The
cost based SQL optimizer
is a component of an ORACLE DBMS that scrutinizes SQL
statements and searches for an optimal execution plan. It calculates a cost for feasible plans
and chooses the plan with the lowest cost.
Current read
Read access to a block with current data, as opposed to a
consistent read
, which may not
retrieve the most current data.
Cursor
Strictly speaking, a
cursor
is a control structure for the iterative traversal of rows in a query
result set. In ORACLE server parlance, cursors are used to execute any SQL or PL/SQL state-
ment.
Data Definition Language (DDL)
SQL statements that create database objects such as tables and indexes.
Database
A
database
is a structured collection of records or data that is stored on a computer system,
such that a program (
Database Management System
) can consult it to answer queries. An
ORACLE database consists of control file(s), redo log files, and data files.
Database Management System (DBMS)
A DBMS is a set of software programs that controls the storage, management, and retrieval
of data in a
database
.
Data Manipulation Language (DML)
SQL statements that retrieve and modify database data. DML statements include
SELECT
,
INSERT
,
MERGE
,
UPDATE
, and
DELETE
.
Database call
A database call is a
parse
,
execute
, or
fetch
operation that an ORACLE server process performs
for servicing a request from a database client.
Dynamic performance view (V$ fixed view)
Views that for the most part expose the inner workings of an ORACLE DBMS and provide
access to performance metrics. The names of these views start with V$. V$ fixed views are
not associated with segments in a database. Many are based on memory structures in the
SGA and are thus “dynamic”. Others are based on control file record sections.
