Wednesday, September 5, 2007

The architecture of an Oracle 10g database

The architecture of an Oracle 10g database

Learning objective

After completing this topic, you should be able to distinguish between the basic components of Oracle database architecture.

Exercise overview

In this exercise, you're required to identify and distinguish between the files, memory structures, processes, and tools in Oracle Database 10g.

This involves the following tasks:

  • identifying database core files
  • distinguishing between storage units
  • recognizing memory areas
  • distinguishing between processes
  • recognizing elements of the data dictionary

Task 1: Identifying database core files

You are a database administrator and your company is changing over to Oracle Database 10g. You want to refresh your knowledge of the architecture and framework of Oracle Database 10g.

First, you have to make sure you know what the constituent files of the database are.

Step 1 of 5

Which of these files make up the core files of an Oracle database?

Options:

  1. Archive log files
  2. Control files
  3. Data files
  4. Redo log files

Result

The Oracle database is made up of control files, data files, and redo log files.

Option 1 is incorrect. While the archive log files are part of the database, and contain an ongoing history of the redo logs, they are not database core files.

Option 2 is correct. Control files contain data about the status of the physical data files stored in the database.

Option 3 is correct. Data is stored in the database in data files. The database is made up of one or more tablespaces, each of which can contain one or more data files.

Option 4 is correct. Redo log files are used to help recover database instances if the original data is lost due to a system failure, such as a power outage or a computer fault.

Task 2: Distinguishing between storage units

Now, you want to refamiliarize yourself with how data is stored in Oracle Database 10g.

Step 2 of 5

Match the storage units to the appropriate descriptions.

Options:

  1. Data blocks
  2. Extents
  3. Segments
  4. Tablespaces

Targets:

  1. Used to group related logical structures together
  2. The smallest unit of data used by a database
  3. Used to contain database objects, such as tables and indexes
  4. Made up of contiguous data blocks

Result

Tablespaces are used to group related logical structures together. Data blocks are the smallest unit of data in a database. Segments are used to contain database objects, such as tables and indexes, and extents are made up of contiguous data blocks.

When a set of data blocks is requested by the database, the OS aligns them with real OS blocks on the storage device.

As extents are made up of contiguous data blocks, each extent can only exist in one data file.

A segment is made up of one or more extents.

Tablespaces contain one or more data files, which physically store the data of all the logical structures in the database.

Task 3: Recognizing memory areas

You need to understand how memory areas perform various functions in Oracle Database 10g.

Step 3 of 5

Match the memory areas with their characteristics.

Options:

  1. Where the Oracle instance holds data in buffers and memory caches
  2. Used to store data and control information for each server process
  3. Contains a shared pool, a large pool, a Java pool, and a streams pool
  4. Private to its server process, and is read and written by Oracle code acting on its behalf

Targets:

  1. SGA
  2. PGA

Result

The SGA is where the Oracle instance holds data in buffers and memory caches. It contains a shared pool, a large pool, a Java pool, and a streams pool. The PGA is used to store data and control information for each server process,is private to its server process, and is read and written by Oracle code acting on its behalf.

Task 4: Distinguishing between processes

It's also essential that you know the difference between a background process and a server process.

Step 4 of 5

Which of these are background processes?

Options:

  1. Checkpoint
  2. Database writer
  3. Enterprise Manager
  4. Process monitor

Result

Checkpoint, database writer, and process monitor are all background processes.

Option 1 is correct. The checkpoint tells the database writer about data changes. It also informs the database's data files and control files about the most recent checkpoint.

Option 2 is correct. The database writer is used to write the changed data from the database buffer cache to the long-term store on the hard disk.

Option 3 is incorrect. The Enterprise Manager is not a background process, it is an Oracle tool. When invoked, it creates a server request.

Option 4 is correct. When a user process fails, the process cleanup is performed by the process monitor.

Task 5: Recognizing elements of the data dictionary

Finally, you should understand how the data dictionary functions in Oracle Database 10g.

Step 5 of 5

Which of these are characteristic elements of the data dictionary?

Options:

  1. It's created at the same time as the database
  2. It's updated when the structure of the database is updated
  3. It performs crash recovery
  4. It is used by Enterprise Manager to show information about tables and views

Result

The data dictionary is created when the database is created, and it's updated whenever the database is modified. It's also used by the Enterprise Manager to show information about tables and views.

Option 1 is correct. The data dictionary is a read-only reference containing information about the sets of tables and views in a particular database.

Option 2 is correct. The data dictionary also contains the allocated space for a schema object and the amount currently in use.

Option 3 is incorrect. It is the system monitor, a background process in the PGA, that performs crash recovery.

Option 4 is correct. The DICTIONARY view in the Enterprise Manager provides useful descriptions of the data dictionary tables and views.

2 comments:

Diva said...

Base of 10g., really nice and simple keep it up., can i get ur full details my friend !!

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