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

参考：http://blog.csdn.net/rlhua/article/details/13998311

LOG_ARCHIVE_MIN_SUCCEED_DEST=2 这里的意思是至少要2个archive destination成功，日志归档才会成功。
如果LOG_ARCHIVE_DEST_1不能访问，会被忽略