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为防止在使用RESETLOGS选项进行恢复时覆盖旧的日志文件，文章详细介绍了如何设置LOG_ARCHIVE_FORMAT参数，通过包含特定变量如%t(线程号)，%s(日志序列号)和%r(resetlogs ID)来生成唯一的归档日志文件名。

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In your database, you may be forced to perform a recovery using the RESETLOGS option during which the redo logs would be reset to sequence number 1. You want to avoid the overwriting of old log files.

Which archived log file name format ensures this?

A. %t_%s.dbf

B. arch_%t.arc

C. arch_%d.arc

D. arch_%t_%d.arc

E. arch_%d_%s_.dbf

F. arch_%t_%s_%r.arc

Answer: F

Automatic Recovery with the RECOVER Command

LOG_ARCHIVE_FORMAT = arch_%t_%s_%r.arc

　　In this example, SQL*Plus automatically suggests the file name /arc_dest/loc2/arch_%t_%s_%r.arc (where %t is the thread, %s is the sequence and %r is the resetlogs ID).

Setting Initialization Parameters for Archive Destinations

　　Optionally, set the LOG_ARCHIVE_FORMAT initialization parameter, using %t to include the thread number as part of the file name, %s to include the log sequence number, and %r to include the resetlogs ID (a timestamp value represented in ub4). Use capital letters (%T, %S, and %R) to pad the file name to the left with zeroes.

Note:

If the COMPATIBLE initialization parameter is set to 10.0.0 or higher, the database requires the specification of resetlogs ID ( %r) when you include the LOG_ARCHIVE_FORMAT parameter. The default for this parameter is operating system dependent.

The incarnation of a database changes when you open it with the RESETLOGS option. Specifying %r causes the database to capture the resetlogs ID in the archived redo log file name. See Oracle Database Backup and Recovery User's Guide for more information about this method of recovery.

The following example shows a setting of LOG_ARCHIVE_FORMAT:

LOG_ARCHIVE_FORMAT = arch_%t_%s_%r.arc

This setting will generate archived logs as follows for thread 1; log sequence numbers 100, 101, and 102; resetlogs ID 509210197. The identical resetlogs ID indicates that the files are all from the same database incarnation:

/disk1/archive/arch_1_100_509210197.arc, 
/disk1/archive/arch_1_101_509210197.arc, 
/disk1/archive/arch_1_102_509210197.arc

/disk2/archive/arch_1_100_509210197.arc, 
/disk2/archive/arch_1_101_509210197.arc, 
/disk2/archive/arch_1_102_509210197.arc

/disk3/archive/arch_1_100_509210197.arc, 
/disk3/archive/arch_1_101_509210197.arc, 
/disk3/archive/arch_1_102_509210197.arc

转载于:https://www.cnblogs.com/Babylon/p/8622211.html