從Oracle11gR2 開始，在備份控制檔案時，不在需要鎖住controlfile enqueue。對於非RAC 的資料庫，沒有任何改變，但對於RAC 資料庫，因為控制檔案備份機制的改變，叢集中的任何instance 可以需要寫入到快照控制檔案，因此snapshot controlfile需要對所有例項是可見的。

在RAC 環境下，如果snapshot controlfile 不在共享的位置，控制檔案任何形式的都可能報ORA-245的錯誤。

快照控制檔案必須能被所有節點訪問，如果快照控制不是存放在共享裝置上，那麼在RMAN 進行控制檔案的快照備份時就會報錯。

Changes

RAC Database release 11.2

Cause

The error description is:

00245, 00000, "control file backup failed; target is likely on a local file system"

// *Cause: Failed to create a control file backup because some process

// signaled an error during backup creation. This is likely caused

// by the backup target being on a local file system so it could not

// be accessed by other instances. It can also be caused by other

// I/O errors to the backup target. Any process of any instance that

// starts a read/write control file transaction must have access

// to the backup control file during backup creation.

// *Action: Check alert files of all instances for further information.

RMAN creates a copy of the control file for read consistency, this is the snapshot controlfile.

Due to the changes made to the controlfile backup mechanism in 11gR2 any instances

in the cluster may write to the snapshot controlfile. Therefore,

the snapshot controlfile file needs to be visible to all instances.

The same happens when a backup of the controlfile is

created directly from sqlplus any instance in the cluster may write to the backup controfile file.

In 11gR2 onwards, the controlfile backup happens without holding the control file enqueue.

For non-RAC database, this doesn't change anything.

But, for RAC database, the snapshot controlfile location must be

in a shared file system that will be accessible from all the nodes.

The snapshot controlfile MUST be accessible by all nodes of a RAC database.

Solution

The snapshot controlfile MUST be accessible by all nodes of a RAC database,

if the snapshot controlfile does not reside in on a shared device this error will raise.

1. Check the snapshot controlfile location:

RMAN> show all;

2. Configure the snapshot controlfile to a shared disk:

解決方案：

配置snapshot controlfile 到共享位置

CONFIGURE SNAPSHOT CONTROLFILENAME TO '<shared_disk>/snapcf_<DBNAME>.f';

如果使用了ASM，就指定到對應的ASM disk group：

CONFIGURE SNAPSHOT CONTROLFILENAME TO '+<DiskGroup>/snapcf_<DBNAME>.f';

例子：

RMAN> show all

2> ;

using target database control file instead of recovery catalog

RMAN configuration parameters for database with db_unique_name RACDB are:

CONFIGURE RETENTION POLICY TO REDUNDANCY 14;

CONFIGURE BACKUP OPTIMIZATION OFF; # default

CONFIGURE DEFAULT DEVICE TYPE TO DISK; # default

CONFIGURE CONTROLFILE AUTOBACKUP OFF; # default

CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '%F'; # default

CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO BACKUPSET; # default

CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default

CONFIGURE ARCHIVELOG BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default

CONFIGURE MAXSETSIZE TO UNLIMITED; # default

CONFIGURE ENCRYPTION FOR DATABASE OFF; # default

CONFIGURE ENCRYPTION ALGORITHM 'AES128'; # default

CONFIGURE COMPRESSION ALGORITHM 'BASIC' AS OF RELEASE 'DEFAULT' OPTIMIZE FOR LOAD TRUE ; # default

CONFIGURE ARCHIVELOG DELETION POLICY TO NONE; # default

CONFIGURE SNAPSHOT CONTROLFILE NAME TO '/u01/oracle/11g/dbs/snapcf_RACDB1.f'; # default

RMAN> CONFIGURE SNAPSHOT CONTROLFILE NAME TO '+DATA1/snapcf_RACBD.F';

old RMAN configuration parameters:

CONFIGURE SNAPSHOT CONTROLFILE NAME TO '+DATA1/snapcf.f';

new RMAN configuration parameters:

CONFIGURE SNAPSHOT CONTROLFILE NAME TO '+DATA1/snapcf_RACBD.F';

new RMAN configuration parameters are successfully stored