104 DBMS_STORAGE_MAP

With the DBMS_STORAGE_MAP package, you can communicate with the Oracle background process FMON to invoke mapping operations that populate mapping views. FMON communicates with operating and storage system vendor-supplied mapping libraries.

This chapter contains the following topics:

Using DBMS_STORAGE_MAP
- Overview
- Operational Notes
Summary of DBMS_STORAGE_MAP Subprograms

Overview

The following terminology and descriptions will help you understand the DBMS_STORAGE_MAP API:

Mapping libraries

Mapping libraries help you map the components of I/O processing stack elements. Examples of I/O processing components include files, logical volumes, and storage array I/O targets. The mapping libraries are identified in filemap.ora.
Mapping files

A mapping file is a mapping structure that describes a file. It provides a set of attributes, including file size, number of extents that the file is composed of, and file type.
Mapping elements and sub-elements

A mapping element is the abstract mapping structure that describes a storage component within the I/O stack. Examples of elements include mirrors, stripes, partitions, raid5, concatenated elements, and disks—structures that are the mapping building blocks. A mapping sub-element describes the link between an element and the next elements in the I/O mapping stack
Mapping file extents

A mapping file extent describes a contiguous chunk of blocks residing on one element. This includes the device offset, the extent size, the file offset, the type (data or parity), and the name of the element where the extent resides. In the case of a raw device or volume, the file is composed of only one file extent component. A mapping file extent is different from Oracle extents.
See Also:
- Oracle Database Administrator's Guide for more information
- Oracle Database Reference for V$MAP views, including V$MAP_FILE, V$MAP_ELEMENT, V$MAP_SUBELEMENT, V$MAP_FILE_EXTENT

Operational Notes

For MAP_ELEMENT, MAP_FILE, and MAP_ALL: Invoking these functions when mapping information already exists will refresh the mapping if configuration IDs are supported. If configuration IDs are not supported, then invoking these functions again will rebuild the mapping.

Summary of DBMS_STORAGE_MAP Subprograms

Table 104-1 DBMS_STORAGE_MAP Package Subprograms

Subprogram	Description
DROP_ALL Function	Drops all mapping information in the shared memory of the instance
DROP_ELEMENT Function	Drops the mapping information for the element defined by `elemname`
DROP_FILE Function	Drops the file mapping information defined by `filename`
LOCK_MAP Procedure	Locks the mapping information in the shared memory of the instance
MAP_ALL Function	Builds the entire mapping information for all types of Oracle files (except archive logs), including all directed acyclic graph (DAG) elements
MAP_ELEMENT Function	Builds mapping information for the element identified by `elemname`
MAP_FILE Function	Builds mapping information for the file identified by `filename`
MAP_OBJECT Function	Builds the mapping information for the Oracle object identified by the object name, owner, and type
RESTORE Function	Loads the entire mapping information from the data dictionary into the shared memory of the instance
SAVE Function	Saves information needed to regenerate the entire mapping into the data dictionary
UNLOCK_MAP Procedure	Unlocks the mapping information in the shared memory of the instance.

DROP_ALL Function

This function drops all mapping information in the shared memory of the instance.

Syntax

DBMS_STORAGE_MAP.DROP_ALL(
      dictionary_update IN BOOLEAN DEFAULT TRUE);

Parameters

Table 104-2 DROP_ALL Function Parameters

Parameter	Description
`dictionary_update`	If `TRUE`, mapping information in the data dictionary is updated to reflect the changes. The default value is `TRUE`; `dictionary_update` is an overloaded argument.

DROP_ELEMENT Function

This function drops the mapping information for the element defined by elemname.

Syntax

DBMS_STORAGE_MAP.DROP_ELEMENT(
   elemname          IN VARCHAR2,
   cascade           IN BOOLEAN,
   dictionary_update IN BOOLEAN DEFAULT TRUE);

Parameters

Table 104-3 DROP_ELEMENT Function Parameters

Parameter	Description
`elemname`	The element for which mapping information is dropped.
`cascade`	If `TRUE`, then `DROP_ELEMENT` is invoked recursively on all elements of the DAG defined by `elemname,` if possible.
`dictionary_update`	If `TRUE`, mapping information in the data dictionary is updated to reflect the changes. The default value is `TRUE`; `dictionary_update` is an overloaded argument.

DROP_FILE Function

This function drops the file mapping information defined by filename.

Syntax

DBMS_STORAGE_MAP.DROP_FILE(
   filename          IN VARCHAR2,
   cascade           IN BOOLEAN,
   dictionary_update IN BOOLEAN DEFAULT TRUE);

Parameters

Table 104-4 DROP_FILE Function Parameters

Parameter	Description
`filename`	The file for which file mapping information is dropped.
`cascade`	If `TRUE`, then the mapping DAGs for the elements where the file resides are also dropped, if possible.
`dictionary_update`	If `TRUE`, mapping information in the data dictionary is updated to reflect the changes. The default value is `TRUE`; `dictionary_update` is an overloaded argument.

LOCK_MAP Procedure

This procedure locks the mapping information in the shared memory of the instance. This is useful when you need a consistent snapshot of the V$MAP tables. Without locking the mapping information, V$MAP_ELEMENT and V$MAP_SUBELEMENT, for example, may be inconsistent.

Syntax

DBMS_STORAGE_MAP.LOCK_MAP;

MAP_ALL Function

This function builds the entire mapping information for all types of Oracle files (except archive logs), including all directed acyclic graph (DAG) elements. It obtains the latest mapping information because it explicitly synchronizes all mapping libraries.

Syntax

DBMS_STORAGE_MAP.MAP_ALL(
   max_num_fileext   IN NUMBER DEFAULT 100,
   dictionary_update IN BOOLEAN DEFAULT TRUE);

Parameters

Table 104-5 MAP_ALL Function Parameters

Parameter	Description
`max_num_fileext`	Defines the maximum number of file extents to be mapped. This limits the amount of memory used when mapping file extents. The default value is `100`; `max_num_fileextent` is an overloaded argument.
`dictionary_update`	If `TRUE`, mapping information in the data dictionary is updated to reflect the changes. The default value is `TRUE`; `dictionary_update` is an overloaded argument.

Usage Notes

You must explicitly call MAP_ALL in a cold startup scenario.

MAP_ELEMENT Function

This function builds mapping information for the element identified by elemname. It may not obtain the latest mapping information if the element being mapped, or any one of the elements within its I/O stack (if cascade is TRUE), is owned by a library that must be explicitly synchronized.

Syntax

DBMS_STORAGE_MAP.MAP_ELEMENT(
   elemname          IN VARCHAR2,
   cascade           IN BOOLEAN,
   dictionary_update IN BOOLEAN DEFAULT TRUE);

Parameters

Table 104-6 MAP_ELEMENT Function Parameters

Parameter	Description
`elemname`	The element for which mapping information is built.
`cascade`	If `TRUE`, all elements within the elemname I/O stack DAG are mapped.
`dictionary_update`	If `TRUE`, mapping information in the data dictionary is updated to reflect the changes. The default value is `TRUE`; `dictionary_update` is an overloaded argument.

MAP_FILE Function

This function builds mapping information for the file identified by filename. Use this function if the mapping of one particular file has changed. The Oracle database server does not have to rebuild the entire mapping.

Syntax

DBMS_STORAGE_MAP.MAP_FILE(
   filename           IN VARCHAR2, 
   filetype           IN VARCHAR2,
   cascade            IN BOOLEAN,
   max_num_fileextent IN NUMBER DEFAULT 100,
   dictionary_update  IN BOOLEAN DEFAULT TRUE);

Parameters

Table 104-7 MAP_FILE Function Parameters

Parameter	Description
`filename`	The file for which mapping information is built.
`filetype`	Defines the type of the file to be mapped. It can be "`DATAFILE", "SPFILE", "TEMPFILE", "CONTROLFILE", "LOGFILE",` or `"ARCHIVEFILE"`.
`cascade`	Should be `TRUE` only if a storage reconfiguration occurred. For all other instances, such as file resizing (either through an `ALTER SYSTEM` command or DML operations on extended files), `cascade` can be set to `FALSE` because the mapping changes are limited to the file extents only. If `TRUE`, mapping DAGs are also built for the elements where the file resides.
`max_num_fileextent`	Defines the maximum number of file extents to be mapped. This limits the amount of memory used when mapping file extents. The default value is `100`; `max_num_fileextent` is an overloaded argument.
`dictionary_update`	If `TRUE`, mapping information in the data dictionary is updated to reflect the changes. The default value is `TRUE`; `dictionary_update` is an overloaded argument.

Usage Notes

This function may not obtain the latest mapping information if the file being mapped, or any one of the elements within its I/O stack (if cascade is TRUE), is owned by a library that must be explicitly synchronized.

MAP_OBJECT Function

This function builds the mapping information for the Oracle object identified by the object name, owner, and type.

Syntax

DBMS_STORAGE_MAP.MAP_OBJECT(
   objname  IN  VARCHAR2,
   owner    IN  VARCHAR2,
   objtype  IN  VARCHAR2);

Parameters

Table 104-8 MAP_OBJECT Function Parameters

Parameter	Description
`objname`	The name of the object.
`owner`	The owner of the object.
`objtype`	The type of the object.

RESTORE Function

This function loads the entire mapping information from the data dictionary into the shared memory of the instance. You can invoke RESTORE only after a SAVE operation. You must explicitly call RESTORE in a warm startup scenario.

Syntax

DBMS_STORAGE_MAP.RESTORE;

SAVE Function

This function saves information needed to regenerate the entire mapping into the data dictionary.

Syntax

DBMS_STORAGE_MAP.SAVE;

UNLOCK_MAP Procedure

This procedure unlocks the mapping information in the shared memory of the instance.

Syntax

DBMS_STORAGE_MAP.UNLOCK_MAP;