Oracle 11g高效稳健的存储机制（oracle 11g存储）

Oracle 11g: Efficient and Robust Storage Mechanism

Oracle 11g is a database management system designed to incorporate high-performance, reliability, and easy scalability for enterprise-level applications. The database’s storage mechanism plays a crucial role in enabling these features. This article discusses the Oracle 11g storage architecture and how it works to ensure efficient and robust data management.

Oracle 11g Storage Architecture

The storage architecture of Oracle 11g comprises the following components:

1. Tablespace: This is a logical unit of storage that contns one or more database files. A database can have multiple tablespaces, and each tablespace can have multiple data files. Tablespace provides a structure to partition database files logically.

2. Datafile: This is a physical storage file that holds data from a tablespace. A tablespace can have one or more data files. Each data file should be allocated using the operating system’s file management system.

3. Segments: A segment is a logical unit of a table or index. A table segment holds table data, while an index segment holds index data. Multiple segments of a table or index can exist in different tablespaces.

4. Extents: An extent is a contiguous space allocated to a segment for storing data. Each extent can hold a specific number of data blocks. A segment can have multiple extents.

5. Blocks: Blocks are the smallest units of storage in Oracle 11g. A block size can vary from 2KB to 32KB. Each block holds a specific number of rows and columns of a table or index. Blocks are stored in extents.

Oracle 11g Storage Mechanism

Oracle 11g uses a multi-tier architecture to manage data storage. It comprises three layers:

1. Physical storage layer: This layer consists of data files, which are stored in storage devices such as hard disk drives (HDD) and solid-state drives (SSD). Oracle 11g uses the operating system’s file management system to control physical file storage.

2. Logical storage layer: This layer consists of tablespaces, segments, extents, and blocks. Oracle 11g uses the logical storage layer to manage the physical files stored in the physical storage layer.

3. Memory storage layer: This layer holds data in memory temporarily. Oracle 11g has several memory structures, such as the buffer cache, shared pool, and redo log buffer, to store data in memory.

Oracle 11g storage mechanism uses a technique called Automatic Storage Management (ASM) to provide efficient storage management. ASM simplifies the process of allocating storage space and improves the database’s overall performance. ASM supports several features such as compression, mirroring, and striping to enhance the reliability and avlability of the data.

The following code demonstrates how to create a table in Oracle 11g:

CREATE TABLE employees (

employee_id number(10) not null,

first_name varchar2(50),

last_name varchar2(50) not null,

eml varchar2(150) not null,

phone_number varchar2(50),

hire_date date not null,

job_id varchar2(50) not null,

salary number(8,2),

commission_pct number(2,2),

manager_id number(10),

department_id number(10)

);

The above code creates a table named “employees” with various columns such as employee_id, first_name, last_name, etc. The table’s columns define the types of data they hold and any constrnts such as NOT NULL, PRIMARY KEY, UNIQUE, etc.

Conclusion

Oracle 11g’s storage mechanism plays a vital role in managing large and complex databases. The storage architecture comprises logical and physical storage layers, which work together to ensure efficient and robust data management. The Automatic Storage Management (ASM) feature simplifies the process of allocating storage space and improves the database’s overall performance. The above code snippet demonstrates how to create a table in Oracle 11g using SQL.