Lesson 1 Objectives After completing this lesson,you should be able to do the follwing: 1.Outline the Oracle architecture and its main components 2.List the structures involved in connecting a user to an Oracle Instance Oracle Server An Oracle server: 1.Is a database management system that provides an open,comprehensive,integrated approach to information management . 2.Consists of an Oracle instance and an Oracle database. a).startup nomount b).alter database mount c).alter database opensystem global area instance-- Memory structure Background process Database—data file Log file Control file Dictionary cache row chacheOracle Instance An Oracle instance Is a means to access an Oracle database Always opens one and only one database Consists of memory and process structuresOracle database An Oracle database: Is a collection of data that is treated as a unit Consists of three file typesMemory Structure Oracle’s memory structure consists of two memory areas knows as: System Global Area(SGA):Allocated at instance startup, and is a fundamental component of an Oracle Instance Program Global Area(PGA):Allocated when the server process is startedSystem Global Area (SGA) The SGA consists of several memory structures: Shared pool Database buffer cache Redo log buffer Other structures(e.g.lock and latch management,statistical data) There are two optional memory structures that can be configured within the SGA: Large pool Java pool SGA is dynamic and sized using SGA_MAX_SIZE. SGA memory allocated and tracked in granules by SGA components --Contiguous virtual memory allocation --Size based on SGA_MAX_SIZELibrary Cache The library cache stores information about the most recently used SQL and PL/SQL statements.The library cache: Enables the sharing of commonly used statements Is managed by a least recently used(LRU) algorithm Consists of two structures: Shared SQL area Shared PL/SQL area Has Its size determined by the shared pool sizing Library Cache The library cache stores information about the most recently used SQL and PL/SQL statements.The library cache: a).Enabled the sharing of commonly used statements b).Is managed by a lease recently used(LRU) algorithm c).Consists of two structures: Shared SQL area Shared PL/SQL area d).Has its size determined by the shared pool sizing 33:30Data Dictionary Cache The data dictionary cache is a collection of the most recently used definitions in the database. It includes information about database files,tables,indexes,columns,users,privileges,and other database objects. During the parse ohase,the sever process looks at the data dictionary for information to resolve object names and validate access. Caching the data dictionary information into memory improves response time on queries. Size id determined by the shared pool sizing.Database Buffer Cache The database buffer cache stores coples of data blocks that have been retrieved from tha data files. It enables great performance gains when you obtain and update data. It is managed through a least recently used(LRU) algorithm. DB_BLOCK_SIZE determines the primary block size.
Objectives
After completing this lesson,you should be able to do the follwing:
1.Outline the Oracle architecture and its main components
2.List the structures involved in connecting a user to an Oracle Instance
Oracle Server
An Oracle server:
1.Is a database management system that provides an open,comprehensive,integrated approach to information management .
2.Consists of an Oracle instance and an Oracle database.
a).startup nomount
b).alter database mount
c).alter database opensystem global area
instance-- Memory structure
Background process
Database—data file
Log file
Control file
Dictionary cache row chacheOracle Instance
An Oracle instance
Is a means to access an Oracle database
Always opens one and only one database
Consists of memory and process structuresOracle database
An Oracle database:
Is a collection of data that is treated as a unit
Consists of three file typesMemory Structure
Oracle’s memory structure consists of two memory areas knows as:
System Global Area(SGA):Allocated at instance startup, and is a fundamental component of an Oracle Instance
Program Global Area(PGA):Allocated when the server process is startedSystem Global Area (SGA)
The SGA consists of several memory structures:
Shared pool
Database buffer cache
Redo log buffer
Other structures(e.g.lock and latch management,statistical data)
There are two optional memory structures that can be configured within the SGA:
Large pool
Java pool
SGA is dynamic and sized using SGA_MAX_SIZE.
SGA memory allocated and tracked in granules by SGA components
--Contiguous virtual memory allocation
--Size based on SGA_MAX_SIZELibrary Cache
The library cache stores information about the most recently used SQL and PL/SQL statements.The library cache:
Enables the sharing of commonly used statements
Is managed by a least recently used(LRU) algorithm
Consists of two structures:
Shared SQL area
Shared PL/SQL area
Has Its size determined by the shared pool sizing
Library Cache
The library cache stores information about the most recently used SQL and PL/SQL statements.The library cache:
a).Enabled the sharing of commonly used statements
b).Is managed by a lease recently used(LRU) algorithm
c).Consists of two structures:
Shared SQL area
Shared PL/SQL area
d).Has its size determined by the shared pool sizing 33:30Data Dictionary Cache
The data dictionary cache is a collection of the most recently used definitions in the database.
It includes information about database files,tables,indexes,columns,users,privileges,and other database objects.
During the parse ohase,the sever process looks at the data dictionary for information to resolve object names and validate access.
Caching the data dictionary information into memory improves response time on queries.
Size id determined by the shared pool sizing.Database Buffer Cache
The database buffer cache stores coples of data blocks that have been retrieved from tha data files.
It enables great performance gains when you obtain and update data.
It is managed through a least recently used(LRU) algorithm.
DB_BLOCK_SIZE determines the primary block size.