Oracle管理文件OMF （oracle managed files）

2022-01-20 19:08:49

简化dba的管理操作

1：启用 omf

23:16:04 SYS@orcl> show parameter DB_CREATE_FILE_DEST

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

db_create_file_dest                  string

23:16:17 SYS@orcl> select distinct t1.name,t2.name datafile_name  ,t.autoextensible from v$tablespace t1,v$datafile t2    ,dba_data_files t where t1.name=t.tablespace_name   and t1.ts# = t2.ts# and t1.name like '%UNDO%'   order by t1.name asc;

NAME                           DATAFILE_NAME                                                                              AUT

------------------------------ ------------------------------------------------------------------------------------------ ---

TBS_29_UNDO                    /u01/app/oracle/oradata/orcl/tbs_29_undo.dbf                                               YES

TBS_30_UNDO                    /u01/app/oracle/oradata/orcl/tbs_30_undo.dbf                                               YES

UNDOTBS1                       /u01/app/oracle/oradata/orcl/undotbs01.dbf                                                 YES

23:16:52 SYS@orcl> alter system set db_create_file_dest='/u01/app/oracle/oradata/orcl/';

System altered.

23:17:40 SYS@orcl> show parameter DB_CREATE_FILE_DEST

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

db_create_file_dest                  string      /u01/app/oracle/oradata/orcl/

23:17:43 SYS@orcl> show parameter create

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

create_bitmap_area_size              integer     8388608

create_stored_outlines               string

db_create_file_dest                  string      /u01/app/oracle/oradata/orcl/

db_create_online_log_dest_1          string

db_create_online_log_dest_2          string

db_create_online_log_dest_3          string

db_create_online_log_dest_4          string

db_create_online_log_dest_5          string

23:17:49 SYS@orcl> ho ls /u01/app/oracle/oradata/orcl/

compress_01.dbf  datafile5.dbf      redo04.log     tbs_02_02.dbf  tbs_08.dbf     tbs_14.dbf     tbs_17_wallet.dbf      tbsp_1.dbf   test02.dbf  undotbs01.dbf

compress_02.dbf  datafilebig_1.dfb  redo4.log      tbs_03.dbf     tbs_09.dbf     tbs_15.dbf     tbs_19_group_temp.dbf  temp_01.dbf  tp1.dbf     undotbs_1.dbf

control01.ctl    example01.dbf      sysaux01.dbf   tbs_04.dbf     tbs_10.dbf     tbs_16_01.dbf  tbs_20_group_temp.dbf  temp_1.dbf   tp2.dbf     undotbs_add.dbf

datafile1.dbf    redo01.log         system01.dbf   tbs_05.dbf     tbs_11.dbf     tbs_16_02.dbf  tbs_29_undo.dbf        temp_2.dbf   ts1.dbf     users01.dbf

datafile3.dbf    redo02.log         tbs_01.dbf     tbs_06.dbf     tbs_12_01.dbf  tbs_17_01.dbf  tbs_30_undo.dbf        temp.dbf     ts2.dbf

datafile4.dbf    redo03.log         tbs_02_01.dbf  tbs_07.dbf     tbs_13.dbf     tbs_17_02.dbf  tbs_example .dbf       test_01.dbf  ts3.dbf

23:19:56 SYS@orcl> create tablespace tbs_31;

Tablespace created.

23:20:27 SYS@orcl> ho ls /u01/app/oracle/oradata/orcl/

compress_01.dbf  datafile5.dbf      redo03.log    tbs_02_01.dbf  tbs_07.dbf     tbs_13.dbf     tbs_17_02.dbf          tbs_example .dbf  test_01.dbf  ts3.dbf

compress_02.dbf  datafilebig_1.dfb  redo04.log    tbs_02_02.dbf  tbs_08.dbf     tbs_14.dbf     tbs_17_wallet.dbf      tbsp_1.dbf        test02.dbf   undotbs01.dbf

control01.ctl    example01.dbf      redo4.log     tbs_03.dbf     tbs_09.dbf     tbs_15.dbf     tbs_19_group_temp.dbf  temp_01.dbf       tp1.dbf      undotbs_1.dbf

datafile1.dbf    ORCL               sysaux01.dbf  tbs_04.dbf     tbs_10.dbf     tbs_16_01.dbf  tbs_20_group_temp.dbf  temp_1.dbf        tp2.dbf      undotbs_add.dbf

datafile3.dbf    redo01.log         system01.dbf  tbs_05.dbf     tbs_11.dbf     tbs_16_02.dbf  tbs_29_undo.dbf        temp_2.dbf        ts1.dbf      users01.dbf

datafile4.dbf    redo02.log         tbs_01.dbf    tbs_06.dbf     tbs_12_01.dbf  tbs_17_01.dbf  tbs_30_undo.dbf        temp.dbf          ts2.dbf

23:20:30 SYS@orcl> select distinct t1.name,t2.name datafile_name  ,t.autoextensible from v$tablespace t1,v$datafile t2    ,dba_data_files t where t1.name=t.tablespace_name   and t1.ts# = t2.ts# and t1.name = 'TBS_31'   order by t1.name asc;

NAME                           DATAFILE_NAME                                                                              AUT

------------------------------ ------------------------------------------------------------------------------------------ ---

TBS_31                         /u01/app/oracle/oradata/orcl/ORCL/datafile/o1_mf_tbs_31_fkhyxsmr_.dbf                      YES

23:21:00 SYS@orcl> ho ls /u01/app/oracle/oradata/orcl/ORCL

datafile

23:21:36 SYS@orcl> ho ls /u01/app/oracle/oradata/orcl/ORCL/datafile

o1_mf_tbs_31_fkhyxsmr_.dbf

23:21:46 SYS@orcl>

23:21:36 SYS@orcl> ho ls /u01/app/oracle/oradata/orcl/ORCL/datafile

o1_mf_tbs_31_fkhyxsmr_.dbf

23:21:46 SYS@orcl> create temporary tablespace tbs_32_temp ;

Tablespace created.

23:23:36 SYS@orcl> select distinct t1.name,t2.name datafile_name  ,t.autoextensible from v$tablespace t1,v$datafile t2    ,dba_data_files t where t1.name=t.tablespace_name   and t1.ts# = t2.ts# and t1.name = 'TBS_32_TEMP'   order by t1.name asc;

no rows selected

23:23:45 SYS@orcl> COL FILE_NAME FOR A60;

23:33:25 SYS@orcl>  COL TABLESPACE_NAME FOR A30;

23:33:26 SYS@orcl> SELECT TABLESPACE_NAME   AS TABLESPACE_NAME  ,FILE_NAME  AS FILE_NAME   ,STATUS  AS STATUS   ,AUTOEXTENSIBLE   AS AUTOEXTENSIBLE   FROM DBA_TEMP_FILES where TABLESPACE_NAME='tbs_32_temp';

no rows selected

23:33:28 SYS@orcl> SELECT TABLESPACE_NAME   AS TABLESPACE_NAME  ,FILE_NAME  AS FILE_NAME   ,STATUS  AS STATUS   ,AUTOEXTENSIBLE   AS AUTOEXTENSIBLE   FROM DBA_TEMP_FILES where TABLESPACE_NAME='TBS_32_TEMP';

TABLESPACE_NAME                FILE_NAME                                                    STATUS  AUT

------------------------------ ------------------------------------------------------------ ------- ---

TBS_32_TEMP                    /u01/app/oracle/oradata/orcl/ORCL/datafile/o1_mf_tbs_32_t_fk ONLINE  YES

                               hz3rdt_.tmp

23:33:44 SYS@orcl> ho ls /u01/app/oracle/oradata/orcl/ORCL/datafile

o1_mf_tbs_31_fkhyxsmr_.dbf  o1_mf_tbs_32_t_fkhz3rdt_.tmp

23:33:57 SYS@orcl>

What Are Oracle Managed Files?

Using Oracle Managed Files simplifies the administration of an Oracle Database. Oracle Managed Files eliminate the need for you, the DBA, to directly manage the operating system files that comprise an Oracle Database. With Oracle Managed Files, you specify file system directories in which the database automatically creates, names, and manages files at the database object level. For example, you need only specify that you want to create a tablespace; you do not need to specify the name and path of the tablespace's datafile with the DATAFILE clause. This feature works well with a logical volume manager (LVM).

The database internally uses standard file system interfaces to create and delete files as needed for the following database structures:

•Tablespaces

•Redo log files

•Control files

•Archived logs

•Block change tracking files

•Flashback logs

•RMAN backups

Through initialization parameters, you specify the file system directory to be used for a particular type of file. The database then ensures that a unique file, an Oracle managed file, is created and deleted when no longer needed.

This feature does not affect the creation or naming of administrative files such as trace files, audit files, alert logs, and core files.

See Also:

Oracle Automatic Storage Management Administrator's Guide for information about Oracle Automatic Storage Management (Oracle ASM), the Oracle Database integrated file system and volume manager that extends the power of Oracle Managed Files. With Oracle Managed Files, files are created and managed automatically for you, but with Oracle ASM, you get the additional benefits of features such as striping, software mirroring, and dynamic storage configuration, without the need to purchase a third-party logical volume manager.

Who Can Use Oracle Managed Files?

Oracle Managed Files are most useful for the following types of databases:

•Databases that are supported by the following:

◦A logical volume manager that supports striping/RAID and dynamically extensible logical volumes

◦A file system that provides large, extensible files

•Low end or test databases

The Oracle Managed Files feature is not intended to ease administration of systems that use raw disks. This feature provides better integration with operating system functionality for disk space allocation. Since there is no operating system support for allocation of raw disks (it is done manually), this feature cannot help. However, because Oracle Managed Files require that you use the operating system file system (unlike raw disks), you lose control over how files are laid out on the disks and thus, you lose some I/O tuning ability.

What Is a Logical Volume Manager?

A logical volume manager (LVM) is a software package available with most operating systems. Sometimes it is called a logical disk manager (LDM). It allows pieces of multiple physical disks to be combined into a single contiguous address space that appears as one disk to higher layers of software. An LVM can make the logical volume have better capacity, performance, reliability, and availability characteristics than any of the underlying physical disks. It uses techniques such as mirroring, striping, concatenation, and RAID 5 to implement these characteristics.

Some LVMs allow the characteristics of a logical volume to be changed after it is created, even while it is in use. The volume may be resized or mirrored, or it may be relocated to different physical disks.

What Is a File System?

A file system is a data structure built inside a contiguous disk address space. A file manager (FM) is a software package that manipulates file systems, but it is sometimes called the file system. All operating systems have file managers. The primary task of a file manager is to allocate and deallocate disk space into files within a file system.

A file system allows the disk space to be allocated to a large number of files. Each file is made to appear as a contiguous address space to applications such as Oracle Database. The files may not actually be contiguous within the disk space of the file system. Files can be created, read, written, resized, and deleted. Each file has a name associated with it that is used to refer to the file.

A file system is commonly built on top of a logical volume constructed by an LVM. Thus all the files in a particular file system have the same performance, reliability, and availability characteristics inherited from the underlying logical volume. A file system is a single pool of storage that is shared by all the files in the file system. If a file system is out of space, then none of the files in that file system can grow. Space available in one file system does not affect space in another file system. However some LVM/FM combinations allow space to be added or removed from a file system.

An operating system can support multiple file systems. Multiple file systems are constructed to give different storage characteristics to different files as well as to divide the available disk space into pools that do not affect each other.

Benefits of Using Oracle Managed Files

Consider the following benefits of using Oracle Managed Files:

•They make the administration of the database easier.

There is no need to invent filenames and define specific storage requirements. A consistent set of rules is used to name all relevant files. The file system defines the characteristics of the storage and the pool where it is allocated.

•They reduce corruption caused by administrators specifying the wrong file.

Each Oracle managed file and filename is unique. Using the same file in two different databases is a common mistake that can cause very large down times and loss of committed transactions. Using two different names that refer to the same file is another mistake that causes major corruptions.

•They reduce wasted disk space consumed by obsolete files.

Oracle Database automatically removes old Oracle Managed Files when they are no longer needed. Much disk space is wasted in large systems simply because no one is sure if a particular file is still required. This also simplifies the administrative task of removing files that are no longer required on disk and prevents the mistake of deleting the wrong file.

•They simplify creation of test and development databases.

You can minimize the time spent making decisions regarding file structure and naming, and you have fewer file management tasks. You can focus better on meeting the actual requirements of your test or development database.

•Oracle Managed Files make development of portable third-party tools easier.

Oracle Managed Files eliminate the need to put operating system specific file names in SQL scripts.

Oracle Managed Files and Existing Functionality

Using Oracle Managed Files does not eliminate any existing functionality. Existing databases are able to operate as they always have. New files can be created as managed files while old ones are administered in the old way. Thus, a database can have a mixture of Oracle managed and unmanaged files.

Enabling the Creation and Use of Oracle Managed Files

The following table lists the initialization parameters that enable the use of Oracle Managed Files.

Initialization Parameter

Description

DB_CREATE_FILE_DEST

Defines the location of the default file system directory or Oracle ASM disk group where the database creates datafiles or tempfiles when no file specification is given in the create operation. Also used as the default location for redo log and control files ifDB_CREATE_ONLINE_LOG_DEST_n are not specified.

DB_CREATE_ONLINE_LOG_DEST_n

Defines the location of the default file system directory or Oracle ASM disk group for redo log files and control file creation when no file specification is given in the create operation. By changing n, you can use this initialization parameter multiple times, where n specifies a multiplexed copy of the redo log or control file. You can specify up to five multiplexed copies.

DB_RECOVERY_FILE_DEST

Defines the location of the Fast Recovery Area, which is the default file system directory or Oracle ASM disk group where the database creates RMAN backups when no format option is used, archived logs when no other local destination is configured, and flashback logs. Also used as the default location for redo log and control files or multiplexed copies of redo log and control files if DB_CREATE_ONLINE_LOG_DEST_n are not specified.

The file system directories specified by these parameters must already exist; the database does not create them. The directory must also have permissions to allow the database to create the files in it.

The default location is used whenever a location is not explicitly specified for the operation creating the file. The database creates the filename, and a file thus created is an Oracle managed file.

Both of these initialization parameters are dynamic, and can be set using the ALTER SYSTEM or ALTER SESSION statement.

See Also:

•Oracle Database Reference for additional information about initialization parameters

•"How Oracle Managed Files Are Named"

Setting the DB_CREATE_FILE_DEST Initialization Parameter

Include the DB_CREATE_FILE_DEST initialization parameter in your initialization parameter file to identify the default location for the database server to create:

•Datafiles

•Tempfiles

•Redo log files

•Control files

•Block change tracking files

You specify the name of a file system directory that becomes the default location for the creation of the operating system files for these entities. The following example sets /u01/app/oracle/oradata as the default directory to use when creating Oracle Managed Files:

DB_CREATE_FILE_DEST = '/u01/app/oracle/oradata'

Setting the DB_RECOVERY_FILE_DEST Parameter

Include the DB_RECOVERY_FILE_DEST and DB_RECOVERY_FILE_DEST_SIZE parameters in your initialization parameter file to identify the default location for the Fast Recovery Area. The Fast Recovery Area contains:

•Redo log files or multiplexed copies of redo log files

•Control files or multiplexed copies of control files

•RMAN backups (datafile copies, control file copies, backup pieces, control file autobackups)

•Archived logs

•Flashback logs

You specify the name of file system directory that becomes the default location for creation of the operating system files for these entities. For example:

DB_RECOVERY_FILE_DEST = '/u01/app/oracle/fast_recovery_area'

DB_RECOVERY_FILE_DEST_SIZE = 20G

Setting the DB_CREATE_ONLINE_LOG_DEST_n Initialization Parameters

Include the DB_CREATE_ONLINE_LOG_DEST_n initialization parameters in your initialization parameter file to identify the default locations for the database server to create:

•Redo log files

•Control files

You specify the name of a file system directory or Oracle ASM disk group that becomes the default location for the creation of the files for these entities. You can specify up to five multiplexed locations.

For the creation of redo log files and control files only, this parameter overrides any default location specified in the DB_CREATE_FILE_DEST andDB_RECOVERY_FILE_DEST initialization parameters. If you do not specify a DB_CREATE_FILE_DEST parameter, but you do specify the DB_CREATE_ONLINE_LOG_DEST_nparameter, then only redo log files and control files can be created as Oracle Managed Files.

It is recommended that you specify at least two parameters. For example:

DB_CREATE_ONLINE_LOG_DEST_1 = '/u02/oradata'

DB_CREATE_ONLINE_LOG_DEST_2 = '/u03/oradata'

This allows multiplexing, which provides greater fault-tolerance for the redo log and control file if one of the destinations fails.

Creating Oracle Managed Files

If you have met any of the following conditions, then Oracle Database creates Oracle Managed Files for you, as appropriate, when no file specification is given in the create operation:

•You have included any of the DB_CREATE_FILE_DEST, DB_REDOVERY_FILE_DEST, or DB_CREATE_ONLINE_LOG_DEST_n initialization parameters in your initialization parameter file.

•You have issued the ALTER SYSTEM statement to dynamically set any of DB_RECOVERY_FILE_DEST, DB_CREATE_FILE_DEST, or DB_CREATE_ONLINE_LOG_DEST_ninitialization parameters

•You have issued the ALTER SESSION statement to dynamically set any of the DB_CREATE_FILE_DEST, DB_RECOVERY_FILE_DEST, or DB_CREATE_ONLINE_LOG_DEST_ninitialization parameters.

If a statement that creates an Oracle managed file finds an error or does not complete due to some failure, then any Oracle Managed Files created by the statement are automatically deleted as part of the recovery of the error or failure. However, because of the large number of potential errors that can occur with file systems and storage subsystems, there can be situations where you must manually remove the files using operating system commands.

The following topics are discussed in this section:

•How Oracle Managed Files Are Named

•Creating Oracle Managed Files at Database Creation

•Creating Datafiles for Tablespaces Using Oracle Managed Files

•Creating Tempfiles for Temporary Tablespaces Using Oracle Managed Files

•Creating Control Files Using Oracle Managed Files

•Creating Redo Log Files Using Oracle Managed Files

•Creating Archived Logs Using Oracle Managed Files

How Oracle Managed Files Are Named

Note:

The naming scheme described in this section applies only to files created in operating system file systems. The naming scheme for files created in Oracle Automatic Storage Management (Oracle ASM) disk groups is described in Oracle Automatic Storage Management Administrator's Guide.

The filenames of Oracle Managed Files comply with the Optimal Flexible Architecture (OFA) standard for file naming. The assigned names are intended to meet the following requirements:

•Database files are easily distinguishable from all other files.

•Files of one database type are easily distinguishable from other database types.

•Files are clearly associated with important attributes specific to the file type. For example, a datafile name may include the tablespace name to allow for easy association of datafile to tablespace, or an archived log name may include the thread, sequence, and creation date.

No two Oracle Managed Files are given the same name. The name that is used for creation of an Oracle managed file is constructed from three sources:

•The default creation location

•A file name template that is chosen based on the type of the file. The template also depends on the operating system platform and whether or not Oracle Automatic Storage Management is used.

•A unique string created by Oracle Database or the operating system. This ensures that file creation does not damage an existing file and that the file cannot be mistaken for some other file.

As a specific example, filenames for Oracle Managed Files have the following format on a Solaris file system:

destination_prefix/o1_mf_%t_%u_.dbf

where:

•destination_prefix is destination_location/db_unique_name/datafile

where:

◦destination_location is the location specified in DB_CREATE_FILE_DEST

◦db_unique_name is the globally unique name (DB_UNIQUE_NAME initialization parameter) of the target database. If there is no DB_UNIQUE_NAMEparameter, then the DB_NAME initialization parameter value is used.

•%t is the tablespace name.

•%u is an eight-character string that guarantees uniqueness

For example, assume the following parameter settings:

DB_CREATE_FILE_DEST = /u01/app/oracle/oradata

DB_UNIQUE_NAME = PAYROLL

Then an example datafile name would be:

/u01/app/oracle/oradata/PAYROLL/datafile/o1_mf_tbs1_2ixh90q_.dbf

Names for other file types are similar. Names on other platforms are also similar, subject to the constraints of the naming rules of the platform.

The examples on the following pages use Oracle managed file names as they might appear with a Solaris file system as an OMF destination.

Caution:

Do not rename an Oracle managed file. The database identifies an Oracle managed file based on its name. If you rename the file, the database is no longer able to recognize it as an Oracle managed file and will not manage the file accordingly.

Creating Oracle Managed Files at Database Creation

The actions of the CREATE DATABASE statement when using Oracle Managed Files are discussed in this section.

Note:

The rules and defaults in this section also apply to creating a database with Database Configuration Assistant (DBCA). With DBCA, you use a graphical interface to enable Oracle Managed Files and to specify file locations that correspond to the initialization parameters described in this section.

See Also:

Oracle Database SQL Language Reference for a description of the CREATE DATABASE statement

Specifying Control Files at Database Creation

At database creation, the control file is created in the files specified by the CONTROL_FILES initialization parameter. If the CONTROL_FILES parameter is not set and at least one of the initialization parameters required for the creation of Oracle Managed Files is set, then an Oracle managed control file is created in the default control file destinations. In order of precedence, the default destination is defined as follows:

•One or more control files as specified in the DB_CREATE_ONLINE_LOG_DEST_n initialization parameter. The file in the first directory is the primary control file. When DB_CREATE_ONLINE_LOG_DEST_n is specified, the database does not create a control file in DB_CREATE_FILE_DEST or in DB_RECOVERY_FILE_DEST (the Fast Recovery Area).

•If no value is specified for DB_CREATE_ONLINE_LOG_DEST_n, but values are set for both the DB_CREATE_FILE_DEST and DB_RECOVERY_FILE_DEST, then the database creates one control file in each location. The location specified in DB_CREATE_FILE_DEST is the primary control file.

•If a value is specified only for DB_CREATE_FILE_DEST, then the database creates one control file in that location.

•If a value is specified only for DB_RECOVERY_FILE_DEST, then the database creates one control file in that location.

If the CONTROL_FILES parameter is not set and none of these initialization parameters are set, then the Oracle Database default action is operating system dependent. At least one copy of a control file is created in an operating system dependent default location. Any copies of control files created in this fashion are not Oracle Managed Files, and you must add a CONTROL_FILES initialization parameter to any initialization parameter file.

If the database creates an Oracle managed control file, and if there is a server parameter file, then the database creates a CONTROL_FILES initialization parameter entry in the server parameter file. If there is no server parameter file, then you must manually include a CONTROL_FILES initialization parameter entry in the text initialization parameter file.

See Also:

Chapter 11, "Managing Control Files"

Specifying Redo Log Files at Database Creation

The LOGFILE clause is not required in the CREATE DATABASE statement, and omitting it provides a simple means of creating Oracle managed redo log files. If theLOGFILE clause is omitted, then redo log files are created in the default redo log file destinations. In order of precedence, the default destination is defined as follows:

•If either the DB_CREATE_ONLINE_LOG_DEST_n is set, then the database creates a log file member in each directory specified, up to the value of theMAXLOGMEMBERS initialization parameter.

•If the DB_CREATE_ONLINE_LOG_DEST_n parameter is not set, but both the DB_CREATE_FILE_DEST and DB_RECOVERY_FILE_DEST initialization parameters are set, then the database creates one Oracle managed log file member in each of those locations. The log file in the DB_CREATE_FILE_DEST destination is the first member.

•If only the DB_CREATE_FILE_DEST initialization parameter is specified, then the database creates a log file member in that location.

•If only the DB_RECOVERY_FILE_DEST initialization parameter is specified, then the database creates a log file member in that location.

The default size of an Oracle managed redo log file is 100 MB.

Optionally, you can create Oracle managed redo log files, and override default attributes, by including the LOGFILE clause but omitting a filename. Redo log files are created the same way, except for the following: If no filename is provided in the LOGFILE clause of CREATE DATABASE, and none of the initialization parameters required for creating Oracle Managed Files are provided, then the CREATE DATABASE statement fails.

See Also:

Chapter 12, "Managing the Redo Log"

Specifying the SYSTEM and SYSAUX Tablespace Datafiles at Database Creation

The DATAFILE or SYSAUX DATAFILE clause is not required in the CREATE DATABASE statement, and omitting it provides a simple means of creating Oracle managed datafiles for the SYSTEM and SYSAUX tablespaces. If the DATAFILE clause is omitted, then one of the following actions occurs:

•If DB_CREATE_FILE_DEST is set, then one Oracle managed datafile for the SYSTEM tablespace and another for the SYSAUX tablespace are created in theDB_CREATE_FILE_DEST directory.

•If DB_CREATE_FILE_DEST is not set, then the database creates one SYSTEM and one SYSAUX tablespace datafile whose names and sizes are operating system dependent. Any SYSTEM or SYSAUX tablespace datafile created in this manner is not an Oracle managed file.

By default, Oracle managed datafiles, including those for the SYSTEM and SYSAUX tablespaces, are 100MB and autoextensible. When autoextension is required, the database extends the datafile by its existing size or 100 MB, whichever is smaller. You can also explicitly specify the autoextensible unit using the NEXTparameter of the STORAGE clause when you specify the datafile (in a CREATE or ALTER TABLESPACE operation).

Optionally, you can create an Oracle managed datafile for the SYSTEM or SYSAUX tablespace and override default attributes. This is done by including theDATAFILE clause, omitting a filename, but specifying overriding attributes. When a filename is not supplied and the DB_CREATE_FILE_DEST parameter is set, an Oracle managed datafile for the SYSTEM or SYSAUX tablespace is created in the DB_CREATE_FILE_DEST directory with the specified attributes being overridden. However, if a filename is not supplied and the DB_CREATE_FILE_DEST parameter is not set, then the CREATE DATABASE statement fails.

When overriding the default attributes of an Oracle managed file, if a SIZE value is specified but no AUTOEXTEND clause is specified, then the datafile is notautoextensible.

Specifying the Undo Tablespace Datafile at Database Creation

The DATAFILE subclause of the UNDO TABLESPACE clause is optional and a filename is not required in the file specification. If a filename is not supplied and theDB_CREATE_FILE_DEST parameter is set, then an Oracle managed datafile is created in the DB_CREATE_FILE_DEST directory. If DB_CREATE_FILE_DEST is not set, then the statement fails with a syntax error.

The UNDO TABLESPACE clause itself is optional in the CREATE DATABASE statement. If it is not supplied, and automatic undo management mode is enabled (the default), then a default undo tablespace named SYS_UNDOTS is created and a 20 MB datafile that is autoextensible is allocated as follows:

•If DB_CREATE_FILE_DEST is set, then an Oracle managed datafile is created in the indicated directory.

•If DB_CREATE_FILE_DEST is not set, then the datafile location is operating system specific.

See Also:

•"Specifying the SYSTEM and SYSAUX Tablespace Datafiles at Database Creation"

•"Specifying the Undo Tablespace Datafile at Database Creation"

•Chapter 14, "Managing Tablespaces"

CREATE TABLESPACE: Examples

The following are some examples of creating tablespaces with Oracle Managed Files.

See Also:

Oracle Database SQL Language Reference for a description of the CREATE TABLESPACE statement

CREATE TABLESPACE: Example 1 The following example sets the default location for datafile creations to /u01/oradata and then creates a tablespacetbs_1 with a datafile in that location. The datafile is 100 MB and is autoextensible with an unlimited maximum size.

SQL> ALTER SYSTEM SET DB_CREATE_FILE_DEST = '/u01/oradata';

SQL> CREATE TABLESPACE tbs_1;

CREATE TABLESPACE: Example 2 This example creates a tablespace named tbs_2 with a datafile in the directory /u01/oradata. The datafile initial size is 400 MB, and because the SIZE clause is specified, the datafile is not autoextensible.

The following parameter setting is included in the initialization parameter file:

DB_CREATE_FILE_DEST = '/u01/oradata'

The following statement is issued at the SQL prompt:

SQL> CREATE TABLESPACE tbs_2 DATAFILE SIZE 400M;

CREATE TABLESPACE: Example 3 This example creates a tablespace named tbs_3 with an autoextensible datafile in the directory /u01/oradata with a maximum size of 800 MB and an initial size of 100 MB:

The following parameter setting is included in the initialization parameter file:

DB_CREATE_FILE_DEST = '/u01/oradata'

The following statement is issued at the SQL prompt:

SQL> CREATE TABLESPACE tbs_3 DATAFILE AUTOEXTEND ON MAXSIZE 800M;

CREATE TABLESPACE: Example 4 The following example sets the default location for datafile creations to /u01/oradata and then creates a tablespace named tbs_4 in that directory with two datafiles. Both datafiles have an initial size of 200 MB, and because a SIZE value is specified, they are not autoextensible

SQL> ALTER SYSTEM SET DB_CREATE_FILE_DEST = '/u01/oradata';

SQL> CREATE TABLESPACE tbs_4 DATAFILE SIZE 200M, SIZE 200M;

CREATE UNDO TABLESPACE: Example

The following example creates an undo tablespace named undotbs_1 with a datafile in the directory /u01/oradata. The datafile for the undo tablespace is 100 MB and is autoextensible with an unlimited maximum size.

The following parameter setting is included in the initialization parameter file:

DB_CREATE_FILE_DEST = '/u01/oradata'

The following statement is issued at the SQL prompt:

SQL> CREATE UNDO TABLESPACE undotbs_1;

See Also:

Oracle Database SQL Language Reference for a description of the CREATE UNDO TABLESPACE statement

ALTER TABLESPACE: Example

This example adds an Oracle managed autoextensible datafile to the tbs_1 tablespace. The datafile has an initial size of 100 MB and a maximum size of 800 MB.

The following parameter setting is included in the initialization parameter file:

DB_CREATE_FILE_DEST = '/u01/oradata'

The following statement is entered at the SQL prompt:

SQL> ALTER TABLESPACE tbs_1 ADD DATAFILE AUTOEXTEND ON MAXSIZE 800M;

See Also:

Oracle Database SQL Language Reference for a description of the ALTER TABLESPACE statement

Creating Tempfiles for Temporary Tablespaces Using Oracle Managed Files

The following statements that create tempfiles are relevant to the discussion in this section:

•CREATE TEMPORARY TABLESPACE

•ALTER TABLESPACE ... ADD TEMPFILE

When creating a temporary tablespace the TEMPFILE clause is optional. If you include the TEMPFILE clause, then the filename is optional. If the TEMPFILE clause or filename is not provided, then the following rules apply:

•If the DB_CREATE_FILE_DEST initialization parameter is specified, then an Oracle managed tempfile is created in the location specified by the parameter.

•If the DB_CREATE_FILE_DEST initialization parameter is not specified, then the statement creating the tempfile fails.

When you add a tempfile to a tablespace with the ALTER TABLESPACE...ADD TEMPFILE statement the filename is optional. If the filename is not specified, then the same rules apply as discussed in the previous paragraph.

When overriding the default attributes of an Oracle managed file, if a SIZE value is specified but no AUTOEXTEND clause is specified, then the datafile is notautoextensible.

See Also:

"Specifying the Default Temporary Tablespace Tempfile at Database Creation"

CREATE TEMPORARY TABLESPACE: Example

The following example sets the default location for datafile creations to /u01/oradata and then creates a tablespace named temptbs_1 with a tempfile in that location. The tempfile is 100 MB and is autoextensible with an unlimited maximum size.

SQL> ALTER SYSTEM SET DB_CREATE_FILE_DEST = '/u01/oradata';

SQL> CREATE TEMPORARY TABLESPACE temptbs_1;

See Also:

Oracle Database SQL Language Reference for a description of the CREATE TABLESPACE statement

ALTER TABLESPACE... ADD TEMPFILE: Example

The following example sets the default location for datafile creations to /u03/oradata and then adds a tempfile in the default location to a tablespace namedtemptbs_1. The tempfile initial size is 100 MB. It is autoextensible with an unlimited maximum size.

SQL> ALTER SYSTEM SET DB_CREATE_FILE_DEST = '/u03/oradata';

SQL> ALTER TABLESPACE TBS_1 ADD TEMPFILE;

See Also:

Oracle Database SQL Language Reference for a description of the ALTER TABLESPACE statement

Creating Control Files Using Oracle Managed Files

When you issue the CREATE CONTROLFILE statement, a control file is created (or reused, if REUSE is specified) in the files specified by the CONTROL_FILESinitialization parameter. If the CONTROL_FILES parameter is not set, then the control file is created in the default control file destinations. The default destination is determined according to the precedence documented in "Specifying Control Files at Database Creation".

If Oracle Database creates an Oracle managed control file, and there is a server parameter file, then the database creates a CONTROL_FILES initialization parameter for the server parameter file. If there is no server parameter file, then you must create a CONTROL_FILES initialization parameter manually and include it in the initialization parameter file.

If the datafiles in the database are Oracle Managed Files, then the database-generated filenames for the files must be supplied in the DATAFILE clause of the statement.

If the redo log files are Oracle Managed Files, then the NORESETLOGS or RESETLOGS keyword determines what can be supplied in the LOGFILE clause:

•If the NORESETLOGS keyword is used, then the database-generated filenames for the Oracle managed redo log files must be supplied in the LOGFILEclause.

•If the RESETLOGS keyword is used, then the redo log file names can be supplied as with the CREATE DATABASE statement. See "Specifying Redo Log Files at Database Creation".

The sections that follow contain examples of using the CREATE CONTROLFILE statement with Oracle Managed Files.

See Also:

•Oracle Database SQL Language Reference for a description of the CREATE CONTROLFILE statement

•"Specifying Control Files at Database Creation"

CREATE CONTROLFILE Using NORESETLOGS Keyword: Example

The following CREATE CONTROLFILE statement is generated by an ALTER DATABASE BACKUP CONTROLFILE TO TRACE statement for a database with Oracle managed datafiles and redo log files:

CREATE CONTROLFILE
      DATABASE sample
      LOGFILE
        GROUP 1 ('/u01/oradata/SAMPLE/onlinelog/o1_mf_1_o220rtt9_.log',
                 '/u02/oradata/SAMPLE/onlinelog/o1_mf_1_v2o0b2i3_.log')
                  SIZE 100M,
        GROUP 2 ('/u01/oradata/SAMPLE/onlinelog/o1_mf_2_p22056iw_.log',
                 '/u02/oradata/SAMPLE/onlinelog/o1_mf_2_p02rcyg3_.log')
                  SIZE 100M
      NORESETLOGS
      DATAFILE '/u01/oradata/SAMPLE/datafile/o1_mf_system_xu34ybm2_.dbf'
               SIZE 100M,
               '/u01/oradata/SAMPLE/datafile/o1_mf_sysaux_aawbmz51_.dbf'
               SIZE 100M,
               '/u01/oradata/SAMPLE/datafile/o1_mf_sys_undo_apqbmz51_.dbf'
               SIZE 100M
      MAXLOGFILES 5
      MAXLOGHISTORY 100
      MAXDATAFILES 10
      MAXINSTANCES 2
      ARCHIVELOG;

CREATE CONTROLFILE Using RESETLOGS Keyword: Example

The following is an example of a CREATE CONTROLFILE statement with the RESETLOGS option. Some combination of DB_CREATE_FILE_DEST, DB_RECOVERY_FILE_DEST, and DB_CREATE_ONLINE_LOG_DEST_n or must be set.

CREATE CONTROLFILE
      DATABASE sample
      RESETLOGS
      DATAFILE '/u01/oradata/SAMPLE/datafile/o1_mf_system_aawbmz51_.dbf',
               '/u01/oradata/SAMPLE/datafile/o1_mf_sysaux_axybmz51_.dbf',
               '/u01/oradata/SAMPLE/datafile/o1_mf_sys_undo_azzbmz51_.dbf'
      SIZE 100M
      MAXLOGFILES 5
      MAXLOGHISTORY 100
      MAXDATAFILES 10
      MAXINSTANCES 2
      ARCHIVELOG;

Later, you must issue the ALTER DATABASE OPEN RESETLOGS statement to re-create the redo log files. This is discussed in "Using the ALTER DATABASE OPEN RESETLOGS Statement". If the previous log files are Oracle Managed Files, then they are not deleted.

Creating Redo Log Files Using Oracle Managed Files

Redo log files are created at database creation time. They can also be created when you issue either of the following statements:

•ALTER DATABASE ADD LOGFILE

•ALTER DATABASE OPEN RESETLOGS

See Also:

Oracle Database SQL Language Reference for a description of the ALTER DATABASE statement

Using the ALTER DATABASE ADD LOGFILE Statement

The ALTER DATABASE ADD LOGFILE statement lets you later add a new group to your current redo log. The filename in the ADD LOGFILE clause is optional if you are using Oracle Managed Files. If a filename is not provided, then a redo log file is created in the default log file destination. The default destination is determined according to the precedence documented in "Specifying Redo Log Files at Database Creation".

If a filename is not provided and you have not provided one of the initialization parameters required for creating Oracle Managed Files, then the statement returns an error.

The default size for an Oracle managed log file is 100 MB.

You continue to add and drop redo log file members by specifying complete filenames.

See Also:

•"Specifying Redo Log Files at Database Creation"

•"Creating Control Files Using Oracle Managed Files"

Adding New Redo Log Files: Example The following example creates a log group with a member in /u01/oradata and another member in /u02/oradata. The size of each log file is 100 MB.

The following parameter settings are included in the initialization parameter file:

DB_CREATE_ONLINE_LOG_DEST_1 = '/u01/oradata'

DB_CREATE_ONLINE_LOG_DEST_2 = '/u02/oradata'

The following statement is issued at the SQL prompt:

SQL> ALTER DATABASE ADD LOGFILE;

Using the ALTER DATABASE OPEN RESETLOGS Statement

If you previously created a control file specifying RESETLOGS and either did not specify filenames or specified nonexistent filenames, then the database creates redo log files for you when you issue the ALTER DATABASE OPEN RESETLOGS statement. The rules for determining the directories in which to store redo log files, when none are specified in the control file, are the same as those discussed in "Specifying Redo Log Files at Database Creation".

Creating Archived Logs Using Oracle Managed Files

Archived logs are created in the DB_RECOVERY_FILE_DEST location when:

•The ARC or LGWR background process archives an online redo log or

•An ALTER SYSTEM ARCHIVE LOG CURRENT statement is issued.

For example, assume that the following parameter settings are included in the initialization parameter file:

DB_RECOVERY_FILE_DEST_SIZE = 20G

DB_RECOVERY_FILE_DEST = '/u01/oradata'

LOG_ARCHIVE_DEST_1 = 'LOCATION=USE_DB_RECOVERY_FILE_DEST'

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码农公寓

1：启用 omf

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