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This article introduces how to analyze the comprehensive use of ASM/BFT/OMF in Oracle database tablespace design, the content is very detailed, interested friends can refer to, hope to be helpful to you.

In order to meet the comprehensive requirements of high performance and manageability of massive data, many projects will use ASM, OMF and large tablespace technologies in the design of tablespaces.

1. ASM

ASM is a new function in Oracle 10g R2 to simplify the management of Oracle database. It is a volume manager provided by Oracle itself, which is mainly used to replace the LVM provided by the operating system. It not only supports single instance, but also supports RAC very well. ASM automatically manages disk groups and provides effective data redundancy.

ASM provides platform-independent file systems, logical volume management, and soft RAID services. ASM can support striping and disk mirroring, thus adding or removing disks when the database is loaded and automatically balancing IBO to remove "hotspots". It also supports direct and asynchronous Oracle O and uses the Oracle data manager API introduced in Oracle9i (the simplified Imax O system call interface).

ASM structure in RAC Environment

ASM has many benefits to DBA, and using ASM can avoid:

Performance optimization of IPUBO

Data file movement and reorganization

File name management

Logical volume management

File system management

Cluster file system management

Bare equipment management

Interaction between database instance and ASM instance

Using ASM can significantly reduce:

Logical unit number (LUN) management, with a small number of logical units and a large size

Dependence of database administrators on system administrators

Errors that may occur when performing tasks manually

2. BFT

Users can create large file tablespaces in Oracle. In this way, the tablespace used by the Oracle database can consist of a single large file instead of several small data files. This allows Oracle to take advantage of the 64-bit system's ability to create and manage very large files. In a 64-bit system, the storage capacity of the Oracle database has been extended to 8 EB (1EB = 1024PBJ 1PB = 1024TB database 1024GB).

When database files are managed by Oracle and large file tablespaces are used, the data files are completely transparent to the user. In other words, the user only needs to perform administrative operations on the tablespace without worrying about the underlying data files. Use large file tablespaces to make tablespaces the main object of disk space management, backup, and recovery operations. With the use of large file tablespace and the combination of database file management technology by Oracle and automatic storage management technology, it is no longer necessary for administrators to manually create new data files and maintain a large number of database files, thus simplifying database file management.

By default, the data base creates small file tablespaces, the traditional tablespace types in Oracle. SYSTEM and SYSAUX tablespaces in the database are always created using traditional types. Only locally managed and segmented automatically managed tablespaces can use large file tablespaces. But there are two exceptions: locally managed undo tablespaces and temporary tablespaces, even if their segments are manually managed, large file tablespaces can be used. An Oracle database can contain both large and small file tablespaces. The type of tablespace is not considered when the SQL statement is executed, unless the data file name is explicitly referenced in the statement.

The administrator can create a set of temporary tablespaces, and users can take advantage of the temporary space provided by each tablespace in the group when needed. The administrator can also specify the tablespace group as the default temporary tablespace for the database. When users need a lot of temporary space for sorting operations, they can take advantage of large file tablespaces and tablespace groups.

Advantages of using large file tablespaces:

Using large file tablespaces (bigfile tablespace) can significantly enhance the storage capacity of Oracle databases. A small file table space (smallfile tablespace) can contain up to 1024 data files, while a large file table space contains only one file. The maximum capacity of this data file is 1024 times that of small data files. From this point of view, the maximum capacity of large file tablespaces and small file tablespaces is the same. However, because a maximum of 64K data files are used in each database, the limit number of tablespaces in the database when using large file tablespaces is 1024 times that when using small file tablespaces. The total database capacity of using large file tablespaces is three orders of magnitude higher than that of using small file tablespaces. In other words, when an Oracle database uses a large file tablespace and uses the maximum block capacity (32K), its total capacity can reach 8EB.

The use of large file tablespaces in very large databases reduces the number of data files, thus simplifying the management of data files. Due to the reduction of data files, the information about data files in SGA and the capacity of control files (control file) are also reduced.

Because the data file is transparent to the user, the database management is simplified.

Factors to consider when using large file tablespaces:

Large file tablespaces (bigfile tablespace) should be used in conjunction with automatic Storage Management (Automatic Storage Management) or other logical volume management tools (logical volume manager), which should support dynamic extension of logical volumes, as well as striping (distribution of data across disks) or RAID.

You should avoid using large file tablespaces on systems that do not support striping, as this will not facilitate parallel execution (parallel execution) and parallel backup of RMAN (backup parallelization).

Avoid using large file tablespaces when the disk group (disk group) that the tablespace is in use may not have enough space, and the only way to expand the tablespace is to add data files to another diskgroup.

Large file tablespaces are not recommended on platforms that do not support large files, which limits the capacity of tablespaces (tablespace). Refer to the relevant operating system documentation for the maximum file capacity it supports.

If you replace traditional tablespaces with large file tablespaces, the performance of database open (open), checkpoints, and DBWR processes will be improved. However, increasing the capacity of data files (datafile) may increase backup and recovery time.

In a way, large file tablespaces improve the management ability of Oracle on VLDB. Only LMT (Locally Managed Tablespaces) with automatic segment space management supports BIGFILE tablespaces. Large file tablespaces can contain only one file, but files can reach 4G block size.

3. OMF

OMF, the full name is Oracle_Managed Files, that is, Oracle file management, using OMF can simplify the management of administrators, without specifying the name, size, path of the file, its name, size, path is automatically assigned by oracle. When deleting logs, data, and control files that are no longer in use, OMF can also automatically delete their corresponding OS files.

OMF supports automatic management of the following files:

Tablespace

Log files (online)

Control file

Prerequisite: you need to set the relevant parameters for these types of files.

Advantages and disadvantages of OMF:

Advantages: automatic management of condition data files, simple operation and space saving

Disadvantages: reduce the controllability of data files, as an DBA should plan the location, naming rules and initial size of data files when maintaining DB.

OMF is not a new technology of 10g/11g, but it will greatly simplify the database management through the combination of ASM and large tablespace technology.

4. ASM\ BFT\ OMF Comprehensive recommendation

The traditional data system, especially the database system deployed on ORACLE RAC, adopts the classical technical scheme of volume group and bare device, which will lead to the design of a large amount of storage space, such as the design of each table space, data file size, name and the corresponding volume group and bare device. After it is put into operation, because the bare equipment can not be expanded automatically, and the data scale is growing, it will bring a great burden to the later operation and maintenance.

(1) suggestion

In view of the characteristics of those massive systems with large amount of data and large table space, in order to simplify management, it is suggested that ASM, OMF and BFT technology should be used comprehensively. To use OMF, it is recommended that you set the following parameters for the database instance:

DB_CREATE_FILE_DEST='+DATA'

(2) use process and effect evaluation

The comprehensive use of ASM, OMF and BFT technology has the following advantages:

Simplify the creation and deletion scripts of tablespaces without specifying specific data files, such as:

Create bigfile tablespace TS_TAB_TRANSACTIONS datafile size 20G

When you delete a tablespace, the corresponding ASM data files are automatically deleted, such as:

Drop tablespace TS_TAB_TRANSACTIONS including contents

You can automatically expand the tablespace directly without specifying data files:

Alter tablespace TS_TAB_TRANSACTIONS resize 30G; on how to analyze the comprehensive use of ASM/BFT/OMF in the Oracle database tablespace design is shared here, I hope the above content can be of some help to you, can learn more knowledge. If you think the article is good, you can share it for more people to see.

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