Managing Disk Group Templates
- Template Attributes
- Adding Templates to a Disk Group
- Modifying a Disk Group Template
- Dropping Templates from a Disk Group
- Creating Tablespaces in Oracle ASM: Specifying
Attributes with Templates
Templates are used to set attributes of files created in
an Oracle ASM disk group. When a file is created, redundancy and striping
attributes are set for that file based on an explicitly named template or the
system template that is the default template for the file type.
When a disk group is created, Oracle ASM creates a set of
default templates for that disk group. The set consists of one template for
each file type (data file, control file, redo log file, and so on) that is
supported by Oracle ASM. For example, a template named ONLINELOG provides the default file redundancy and striping attributes
for all redo log files written to Oracle ASM disks. Default template settings
depend on the disk group type. The default template for data files for a normal
redundancy disk group sets two-way mirroring, while the corresponding default
template in a high redundancy disk group sets three-way mirroring. You can
modify these default templates.
For example, default redundancy for the online redo log files (ONLINELOG template) for a normal redundancy disk group is MIRROR. In Example 4-1, this setting means that when one copy of a redo log file
extent is written to a disk in failure group controller1, a mirrored copy
of the file extent is written to a disk in failure group controller2. To support the default mirroring of a normal redundancy disk
group, at least two failure groups must be defined.
Table 7-6 lists the default templates and the attributes that are
associated to matching files. As the table shows, the initial redundancy value
of each default template depends on the type of disk group that the template
belongs to.
Using clauses of the ALTER DISKGROUP statement, you can add new templates to a disk group, modify
existing ones, or drop templates. The reason to add templates is to create the
right combination of attributes to meet unique requirements. You can then
reference a template name when creating a file, thereby assigning desired
attributes based on an individual file rather than on the file type.
The V$ASM_TEMPLATE view lists all of the templates known to the Oracle ASM
instance. For an example of the information displayed in the V$ASM_TEMPLATE view, see Example 6-10.
Table 7-4 shows the permitted striping
attribute values and allocation unit size chunks. These values correspond to
the STRIPE column of V$ASM_TEMPLATE.
|
Striping Attribute Value
|
Description
|
|
FINE
|
Striping in 128 KB chunks.
|
|
COARSE
|
Striping in 1 MB chunks.
|
Table 7-5 shows the permitted redundancy values for Oracle ASM templates.
These values correspond to the REDUND column of V$ASM_TEMPLATE.
|
Redundancy Attribute Value
|
Resulting Mirroring in Normal Redundancy Disk Group
|
Resulting Mirroring in High Redundancy Disk Group
|
Resulting Mirroring in External Redundancy Disk Group
|
|
MIRROR
|
Two-way mirroring
|
Three-way mirroring
|
(Not allowed)
|
|
HIGH
|
Three-way mirroring
|
Three-way mirroring
|
(Not allowed)
|
|
UNPROTECTED
|
No mirroring
|
(Not allowed)
|
No mirroring
|
Table 7-6 shows the initial attribute settings for the default templates.
The type of mirroring associated with the Mirroring column for normal,
high, and external redundancy disk groups is specified in Table 7-5. For example, the Mirror column for high redundancy disk
groups displays MIRROR in Table 7-6. In Table 7-5, the MIRROR value for high redundancy disk groups corresponds to Three-way mirroring.
Table 7-6 Oracle ASM system default templates attribute settings
|
Template Name
|
File Striping
|
Mirroring, Normal Redundancy Disk Group
|
Mirroring, High Redundancy Disk Group
|
Mirroring, External Redundancy Disk Group
|
Primary Region
|
Mirror Region
|
|
CONTROLFILE
|
FINE
|
HIGH
|
MIRROR
|
UNPROTECTED
|
COLD
|
MIRRORCOLD
|
|
DATAFILE
|
COARSE
|
MIRROR
|
MIRROR
|
UNPROTECTED
|
COLD
|
MIRRORCOLD
|
|
ONLINELOG
|
COARSE
|
MIRROR
|
MIRROR
|
UNPROTECTED
|
COLD
|
MIRRORCOLD
|
|
ARCHIVELOG
|
COARSE
|
MIRROR
|
MIRROR
|
UNPROTECTED
|
COLD
|
MIRRORCOLD
|
|
TEMPFILE
|
COARSE
|
MIRROR
|
MIRROR
|
UNPROTECTED
|
COLD
|
MIRRORCOLD
|
|
BACKUPSET
|
COARSE
|
MIRROR
|
MIRROR
|
UNPROTECTED
|
COLD
|
MIRRORCOLD
|
|
PARAMETERFILE
|
COARSE
|
MIRROR
|
MIRROR
|
UNPROTECTED
|
COLD
|
MIRRORCOLD
|
|
DATAGUARDCONFIG
|
COARSE
|
MIRROR
|
MIRROR
|
UNPROTECTED
|
COLD
|
MIRRORCOLD
|
|
FLASHBACK
|
COARSE
|
MIRROR
|
MIRROR
|
UNPROTECTED
|
COLD
|
MIRRORCOLD
|
|
CHANGETRACKING
|
COARSE
|
MIRROR
|
MIRROR
|
UNPROTECTED
|
COLD
|
MIRRORCOLD
|
|
DUMPSET
|
COARSE
|
MIRROR
|
MIRROR
|
UNPROTECTED
|
COLD
|
MIRRORCOLD
|
|
XTRANSPORT
|
COARSE
|
MIRROR
|
MIRROR
|
UNPROTECTED
|
COLD
|
MIRRORCOLD
|
|
AUTOBACKUP
|
COARSE
|
MIRROR
|
MIRROR
|
UNPROTECTED
|
COLD
|
MIRRORCOLD
|
|
ASMPARAMETERFILE
|
COARSE
|
MIRROR
|
MIRROR
|
UNPROTECTED
|
COLD
|
MIRRORCOLD
|
|
OCRFILE
|
COARSE
|
MIRROR
|
MIRROR
|
UNPROTECTED
|
COLD
|
MIRRORCOLD
|
Table 7-7 shows the permitted primary and mirror region values for Oracle
ASM templates. These values correspond to the PRIMARY_REGION and MIRROR_REGION columns of V$ASM_TEMPLATE. For more information about disk regions, see "Intelligent Data Placement".
|
Primary and Mirror Region Attribute Value
|
Description
|
|
COLD, MIRRORCOLD
|
Use the inner most tracks (closest to spindle) on the disk
drive.
|
|
HOT, MIRRORHOT
|
Use the outermost tracks which have greater speed and higher bandwidth.
|
If the name of your new template is not listed in Table 7-6, then it is not used as a default template for database file
types. To use the template, you must reference its name when creating a file.
When adding a template to a disk group, the attributes are
optional. If no redundancy attribute is specified, then the value defaults to MIRROR for a normal redundancy disk group, HIGH for a high redundancy disk group, and UNPROTECTED for an external redundancy disk group. If you do not specify a
striping attribute, then the value defaults to COARSE. If you do not
specify a value for the primary or mirror region attributes, then the value
defaults to COLD and MIRRORCOLD respectively.
ALTER DISKGROUP data ADD TEMPLATE reliable
ATTRIBUTES (HIGH FINE);
Example 7-14 creates a new template named unreliable that specifies UNPROTECTED (no mirroring) for files.
ALTER DISKGROUP data ADD TEMPLATE unreliable
ATTRIBUTES (UNPROTECTED);
Note:
Oracle discourages using unprotected files unless you
have implemented hardware mirroring. The previous example is presented only to
further illustrate how the attributes for templates are set.
See Also:
Oracle Database SQL Language Reference for more information about the ALTER DISKGROUP...ADD TEMPLATE command
The MODIFY
TEMPLATE clause of the ALTER DISKGROUP statement enables you to modify the attribute specifications of
an existing system default or user-defined disk group template. Only specified
template attributes are changed. Unspecified properties retain their current
value. When you modify an existing template, only new files created by the
template reflect the attribute changes. Existing files maintain their
attributes.
Example 7-15 changes the striping attribute specification of the reliable template for disk group data.
ALTER DISKGROUP data MODIFY TEMPLATE reliable
ATTRIBUTES (COARSE);
Use the DROP
TEMPLATE clause of the ALTER DISKGROUP statement to drop one or more templates from a disk group. You
can only drop templates that are user-defined; you cannot drop system default
templates.
ALTER DISKGROUP data DROP TEMPLATE unreliable;
Use the SQL ALTER SYSTEM and CREATE TABLESPACE statements to create a tablespace that uses a
user-defined template to specify the attributes of the data file.
ALTER SYSTEM SET DB_CREATE_FILE_DEST =
'+data(mytemplate)';
CREATE TABLESPACE mytblspace;
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