053-511

511.You have configured flash recovery area in your database and you set the following Initialization
parameters for your database instance:
LOG_ARCHIVE_DEST 1 = ,,LOCATION=/disk1/arch MANDATORY'
LOG _ARCHIEVE_DEST 2 = ,,LOCATION=/disk2/arch'
LOG_ARCHIVK_DEST_3 = ,,LOCATION=/diSk3/arch
LOG_ARCH1VK_DEST_4 = ' LOCATION=/disk4/arch'
LOG_ARCHIVE_MIN-SUCCEED_DEST = 2
While the database instance is functional, you realized that the destination set by the
LOG_ARCHIVE_DEST_I parameter Is not available for the archived redo log file to be created in. All redo
log groups have been used. What happens in an event of log switch?
A. The online redo log file Is not allowed to be overwritten.
B. The archived redo log files are written to the flash recovery area until the MANDATORY destination is
made available.
C. The database instance will crash because the archived redo log file cannot be created in a destination
set as MANDATORY.
D. The destination set by the LOG_ARCHIVE_DEST_1 parameter is ignored and the archived redo log
files are created in the next two available locations to guarantee archive log success.
Answer: D

解析:

http://docs.oracle.com/cd/B28359_01/server.111/b28310/archredo006.htm#ADMIN11348

MANDATORY 强制的,表示只有当此路径下日志归档成功后方能覆盖在线日志.

The LOG_ARCHIVE_DEST_n parameter lets you specify whether a destination is OPTIONAL (the default) or MANDATORY. The LOG_ARCHIVE_MIN_SUCCEED_DEST=n parameter uses all MANDATORY destinations plus some number of non-standby OPTIONAL destinations to determine whether LGWR can overwrite the online log. The following rules apply:

• Omitting the MANDATORY attribute for a destination is the same as specifying OPTIONAL. --mandatory被忽略?

• You must have at least one local destination, which you can declare OPTIONAL or MANDATORY. --最小值为1

• When you specify a value for LOG_ARCHIVE_MIN_SUCCEED_DEST=n, Oracle Database will treat at least one local destination as MANDATORY, because the minimum value for LOG_ARCHIVE_MIN_SUCCEED_DEST is 1.

• If any MANDATORY destination fails, including a MANDATORY standby destination, Oracle Database ignores the LOG_ARCHIVE_MIN_SUCCEED_DEST parameter.--这又是什么含义?

• The LOG_ARCHIVE_MIN_SUCCEED_DEST value cannot be greater than the number of destinations, nor can it be greater than the number of MANDATORYdestinations plus the number of OPTIONAL local destinations.

• If you DEFER a MANDATORY destination, and the database overwrites the online log without transferring the archived log to the standby site, then you must transfer the log to the standby manually.