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。而且据说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：
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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.
--
-- Input parameters:
-- cfname
-- Name of file to create or overwrite with the controlfile from the
-- backup set.
PROCEDURE restoreDataFileTo( dfnumber IN binary_integer
,toname IN varchar2 default NULL);
--
-- restoreDataFileTo creates the output file from a complete backup in the
-- backup set.
restore_procedure