作者: Fenng | 可以转载, 但必须以超链接形式标明文章原始出处和作者信息及版权声明网址: http://www.dbanotes.net/database/rman_nocatalog_lost_controlfile_howto.html

情况描述

客户报告数据库故障，新来的系统管理员误操作。删掉了一些文件。具体情况是：删掉了所有重要数据文件、所有控制文件。数据库原来是归档模式，用 RMAN (Recovery Manager) 备份数据，而 RMAN 使用控制文件。幸运的是，最后一次 RMAN full 备份是包括了控制文件在内。系统没有设定自动备份控制文件。现在状况是数据库无法启动。

不用说，客户的备份方案不够完善，但是这时候再去说这些话责备用户有事后诸葛亮之嫌，"用户是上帝，不要去得罪他"。还有，客户有Full备份(虽然不是自动备份控制文件，这样无法用常规的恢复步骤来进行恢复)。这对我们来说是个绝对的好消息。

下面我们通过一次模拟操作来演示这个问题的解决办法。

背景知识

在Oracle 816 以后的版本中,Oracle 提供了一个包: DBMS_BACKUP_RESTORE.DBMS_BACKUP_RESTORE 包是由 dbmsbkrs.sql 和 prvtbkrs.plb 这两个脚本创建的. catproc.sql 脚本运行后会调用这两个包.所以是每个数据库都有的. 这个包是 Oracle 服务器和操作系统之间 IO 操作的接口. 由恢复管理器直接调用。这两个脚本的功能是内建到 Oracle 的一些库文件中的.

由此可见，我们可以在数据库 nomount 情况下调用这些 package ,来达到我们的恢复目的。在dbmsbkrs.sql 和 prvtbkrs.plb 这两个脚本中有详细的说明文档，出于篇幅问题，就不一一加以翻译了，但在下面会直接引用一些原文说明。

关键的内容有：

FUNCTION 　deviceAllocate(

　　　　　　 type IN varchar2 default NULL

　　　　　　,name IN varchar2 default NULL

　　　　　　,ident IN varchar2 default NULL

　　　　　　,noio IN boolean default FALSE

　　　　　　,params IN varchar2 default NULL )

RETURN varchar2;

-- Describe the device to be used for sequential I/O. For device types where

-- only one process at a time can use a device, this call allocates a device

-- for exclusive use by this session. The device remains allocated until

-- deviceDeallocate is called or session termination. The device can be used

-- both for creating and restoring backups.

--

-- Specifying a device allocates a context that exists until the session

-- terminates or deviceDeallocate is called. Only one device can be specified

-- at a time for a particular session. Thus deviceDeallocate must be called

-- before a different device can be specified. This is not a limitation since

-- a session can only read or write one backup at a time.

--

-- The other major effect of allocating a device is to specify the name space

-- for the backup handles (file names). The handle for a sequential file does

-- not necessarily define the type of device used to write the file. Thus it

-- is necessary to specify the device type in order to interpret the file

-- handle. The NULL device type is defined for all systems. It is the file

-- system supplied by the operating system. The sequential file handles are

-- thus normal file names.

--

-- A device can be specified either by name or by type.

-- If the type is specified but not the name, the system picks an

-- available device of that type.

-- If the name is specified but not the type, the type is determined

-- from the device.

-- If neither the type or the name is given, the backups are files in

-- the operating system file system.

-- Note that some types of devices, optical disks for example, can be shared

-- by many processes, and thus do not really require allocation of the device

-- itself. However we do need to allocate the context for accessing the

-- device, and we do need to know the device type for proper interpretation

-- of the file handle. Thus it is always necessary to make the device

-- allocation call before making most other calls in this package.

--

-- Input parameters:

-- type

-- If specified, this gives the type of device to use for sequential

-- I/O. The allowed types are port specific. For example a port may

-- support the type "TAPE" which is implemented via the Oracle tape

-- API. If no type is specified, it may be implied by specifying a

-- particular device name to allocate. The type should be allowed to

-- default to NULL if operating system files are to be used.

--

-- name

-- If specified, this names a particular piece of hardware to use for

-- accessing sequential files. If not specified, any available

-- device of the correct type will be allocated. If the device cannot

-- be shared, it is allocated to this session for exclusive use.

-- The name should be allowed to default to NULL if operating system

-- files are to be used.

--

-- ident

-- This is the users identifier that he uses to name this device. It

-- is only used to report the status of this session via

-- dbms_application_info. This value will be placed in the CLIENT_INFO

-- column of the V$SESSION table, in the row corresponding to the

-- session in which the device was allocated. This value can also

-- be queried with the dbms_application_info.read_client_info procedure.

--

-- noio

-- If TRUE, the device will not be used for doing any I/O. This allows

-- the specification of a device type for deleting sequential files

-- without actually allocating a piece of hardware. An allocation for

-- noio can also be used for issuing device commands. Note that some

-- commands may actually require a physical device and thus will get

-- an error if the allocate was done with noio set to TRUE.

--

-- params

-- This string is simply passed to the device allocate OSD. It is

-- completely port and device specific.

--

-- Returns:

-- It returns a valid device type. This is the type that should be

-- allocated to access the same sequential files at a later date. Note

-- that this might not be exactly the same value as the input string.

-- The allocate OSD may do some translation of the type passed in. The

-- return value is NULL when using operating system files.

PROCEDURE restoreControlfileTo(cfname IN varchar2);

-- This copies the controlfile from the backup set to an operating system

-- file. If the database is mounted, the name must NOT match any of the

-- current controlfiles.

-- 从备份中恢复控制文件为操作系统文件．

-- 如果数据库在 mount 状态，控制文件名字则必须要匹配当前控制文件的名字

-- Input parameters:

-- cfname

-- Name of file to create or overwrite with the controlfile from the

-- backup set.

-- 备份集里的控制文件名字，创建或者覆盖控制文件．

PROCEDURE restoreDataFileTo( dfnumber IN binary_integer

,toname IN varchar2 default NULL);

--

-- restoreDataFileTo creates the output file from a complete backup in the

-- backup set. 

-- 从完整的备份集里创建输出文件

如果您有兴趣可以去阅读一下这两个文件的注释说明．

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