Some Terminologies and their meanings!!! Flashcards
AD-HOC
An Impromptu query.
*select statement/asking for something.
BLOCK
The smallest unit of storage in an oracle database.
Contains:
- The Header information concerning the block itself.
- A Free Space..aka pct free or %Free reserved for UPDATES of rows in the BLOCK.
- Row Data..aka %Used or Pct. Used reserved for Rows.
BUTTLENECK
A system components that limits performance of the system.
BUFFER(memory)
Refers to memories used to store data.
CACHE
Storage area to provide fast access to to data.
CHECKPOINT
I an operation that forces all changed in-memory data blocks to be written out to the disk.
CLEAN BUFFER
An unmodified buffer.
Contains no Data.
CONCURRENCY
Capability of performing many functions at the same time.
DATABASE
Is a set of Data organised for easy access.
**Instance + Physical Files
Instance = SGA + Background Processes.
SGA = System Global Area(Memory Area).
DATA DICTIONARY
Set of tables Oracle uses to maintain information of the Database.
DBA(Database Administrator)
Responsible for operation, configuration and performance of DATA.
RDBMS
Relational Database Management Systems.
Software and collection of tools that manage the Database.
DDL
It is Command for the ability of Creation and Modification of Schema objects.
DIRTY BUFFERS
Found in the database buffer cache.
KINDS OF BUFFER CACHE
There are 3 kinds :
- Clean.
- Pinned.
- Dirty.
DML(Data Manipulation Language)
A command that allows you to query and modify Data within existing Schema objects in a Database.
Data Performance Use - Storing information about performance of thee instance.
Function: Retains ONE result.
A set of SQL or PL/SQL statements used together to execute a particular function.
Procedure: Returns many results after ran.
SQL
PL/SQL
Structured Query Language.
Procedural Language/ Structured Query Language.
PHYSICAL MEMORY
RAM
PACKAGE
Is a collection of procedures and functions.
QUERY
Is a read only transaction against a Database.
To query, you need a Table NAME.
Always start a Query with “select”
First choose *Column and then the *Values.
SCHEMA
Is a collection of OBJECTS associated with the Database.
Schema Objects consists, Clusters, Packages, Indexes, Views, Tables, Synonyms e.tc.
Views are used to secure data.
SGA (System Global Area)
Shared memory region that Oracle uses to store Data and Control information for One Oracle instance.
SGA(Memory)=Shared pool | Buffer Cache | Redo log Buffer.
VIRTUAL MEMORY
This is part of the hard drive and also a temporal memory.
It is a memory that can be used for programming in an Operating System.
When engaged, slows System up and that is called Paging and Swapping.
Data is copied from memory to the swap space.
SQLPLUS
An Oracle utility for connecting into an Oracle Database.
eg: sqlplus *usename/password/@DB connect string.
Logged into a Linux Server as bitechstudent, an O/S user who has no privilege to access the Database. So I must switch user (su -) to one who has access the Database Software ( RDBMS).
su -
enter password oracle11
sqlplus bt/bt (this logs you into the default DB.
desc(ribe) user_tables ( to see all tables owned by the user or schema (bt).
select table_name, NUM_ROWS from user_tables;
[table_name, NUM_ROWS] =Column names
[ user_tables] = table NAME ( Data Dictionary Table)
The select statement issued above will display the NAMES and NUMBER of ROWS of tables OWNED by the current connected USER (bt).
DATA STORAGE
Data is stored in binary form.
Binary Data is 0nes and Zeroes.
Units used to refer to are:
- Bit - Smallest unit of Data Storage.
- Byte - 8 Bits - most commonly used.
- Kilobyte - 1024 Bytes.
