Download 12_Oracle Database Architecture

Oracle Database Architecture
Ashima Wadhwa
Oracle Versions
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E.F.T. Codd implement rules for RDBMS.
Oracle 7 ( Implements 7 Rules)
Oracle 8 (First stable version of Oracle)
9i (integrated with java and supports all
utilities which are used By Java.)
• 10G (Data Grid)
• 11i called Oracle Financials Strong competitor
for SAP and ERP.
Data is Defined as
• A value for an attribute of an entity.
• Entity is Real World Thing which exist and can
be described in terms of one or more
attributes.
• Database is Organized value of all SAME type
of entity.
Memory of ORACLE( Data Dict.)
• Arrangement of system table
stores data about data called
as METADATA.
Storage
LOGICAL
Table
Space
PHYSICAL
Schema
Parameter File,
Control File,
Redo Log File,
Data File
Oracle Database Architecture
Instance
SGA
Shared pool
Server
process
PGA
User
process
DBWR
Parameter
file
Password
file
LGWR
Control files
Redo log
files
Data files
Database
Archived
log files
Oracle Database Architecture
• An Oracle database is a collection of data treated as a unit.
• The purpose of a database is to store and retrieve related
information.
• A database server is the key to solving the problems of
information management. In general, a server reliably
manages a large amount of data in a multiuser
environment so that many users can concurrently access
the same data.
• All this is accomplished while delivering high performance.
• A database server also prevents unauthorized access and
provides efficient solutions for failure recovery.
Oracle Database Architecture
• The database has logical structures and
physical structures. Because the physical and
logical structures are separate, the physical
storage of data can be managed without
affecting the access to logical storage
structures.
Physical Database Structures
• Physical database structures of an Oracle
database, includes :
• Datafiles
• Redo log files
• Control files
• Parameter Files
Data files
• Every Oracle database has one or more
physical data files. The data files contain all
the database data. The data of logical
database structures, such as tables and
indexes, is physically stored in the data files
allocated for a database.
The characteristics of data files are:
• A data file can be associated with only one
database.
• Data files can have certain characteristics set
to let them automatically extend when the
database runs out of space.
• One or more data files form a logical unit of
database storage called a tablespace.
Control File
• Every Oracle database has a control file. A
control file contains entries that specify the
physical structure of the database. For
example, it contains the following
information:
• Database name
• Names and locations of data files and redo log
files
• Time stamp of database creation
Redo Log File
• Oracle used redo base recovery and allow to recover
only committed transaction till the point of failure.
• The redo base recovery in oracle is implemented
through the redo log file.
• When system fails then oracle read history from
these redo log file and guaranties the recovery till
the point of failure.
• These files are created at the creation of oracle db.
• The files are reusable and used as round robin
passion.
• Maximum size is 50Mb.
Redo Log Copies stored to 10 different geographic locations
Redo
log N..
Redo
log 7
Redo
log 6
Redo log 1
Redo
log 5
Redo
log 4
Redo
log 3
Redo log 2
Log Switch
Redo
log 2
Redo
log 1
Parameter Files
• Parameter files contain a list of configuration
parameters for that instance and database.
• Oracle recommends that you create a server
parameter file as a dynamic means of
maintaining initialization parameters. A server
parameter file lets you store and manage your
initialization parameters persistently in a
server-side disk file.
Logical Database Structures
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The logical storage structures, includes :
Tablespace
Data blocks
Extents
Segments
Schema
Tablespaces
• A database is divided into logical storage units called
tablespaces, which group related logical structures
together. For example, tablespaces commonly group
together all application objects to simplify some
administrative operations.
• Each database is logically divided into one or more
tablespaces. One or more datafiles are explicitly
created for each tablespace to physically store the data
of all logical structures in a tablespace. The combined
size of the datafiles in a tablespace is the total storage
capacity of the tablespace.
Oracle Data Blocks
• At the finest level of granularity, Oracle
database data is stored in data blocks. One
data block corresponds to a specific number
of bytes of physical database space on disk.
The standard block size is specified by the
DB_BLOCK_SIZE initialization parameter. In
addition, you can specify up to five other
block sizes. A database uses and allocates free
database space in Oracle data blocks.
Extents
• The next level of logical database space is an
extent. An extent is a specific number of
contiguous data blocks, obtained in a single
allocation, used to store a specific type of
information.
Segments
• Above extents, the level of logical database
storage is a segment. A segment is a set of
extents allocated for a certain logical
structure. The following table describes the
different types of segments.
Types of segments
Data segments - store the table (or cluster) data.
Index segments - store the index data.
Temporary segments - temporary work area e.g. for sorting, executing SQL statements.
Undo (rollback) segments - store undo information. When you roll back changes made
to the database, undo records in the undo tablespace are used to undo the changes.
Schema
• Schema is set of objects own by User Account.
• Each schema has user account but each user
don’t need schema.
• A user account is account with database having
privileges to perform predefined activities on
data.
• Schema may not exist with user account but user
account is exist without schema.
• Purpose : Maintenance of object like backup &
recovery, implementation of security and access
level.
Queries??