LOG_ARCHIVE_DUPLEX_DEST

LOG_ARCHIVE_DUPLEX_DEST

LOG_ARCHIVE_DUPLEX_DEST is similar to the initialization parameter LOG_ARCHIVE_DEST. This parameter specifies a second archive destination: the duplex archive destination. This duplex archive destination can be either a must-succeed or a best-effort archive destination, depending on how many archive destinations must succeed (as specified in the LOG_ARCHIVE_MIN_SUCCEED_DEST parameter).

The default setting of a null string ("") or (' ') indicates that a duplex archive destination does not exist.

大概意思是说 “LOG_ARCHIVE_DUPLEX_DEST”参数是一个保留参数，用于定义归档日志存在的第二个位置。此参数依赖于“LOG_ARCHIVE_MIN_SUCCEED_DEST”定义，规定最小归档日志归档个数。

LOG_ARCHIVE_MIN_SUCCEED_DEST：

LOG_ARCHIVE_MIN_SUCCEED_DEST defines the minimum number of destinations that must succeed in order for the online logfile to be available for reuse.

If you are using the LOG_ARCHIVE_DEST_n parameters and automatic archiving is enabled, the value of this parameter cannot exceed either of the following:

- The total number of destinations

- The number of enabled, valid destinations specified as MANDATORY plus the number of enabled, valid non-standby destinations specified as OPTIONAL

If you are using LOG_ARCHIVE_DEST and LOG_ARCHIVE_DUPLEX_DEST and automatic archiving is enabled, a value of 1 specifies that the destination specified in LOG_ARCHIVE_DEST must succeed. A value of 2 specifies that the destinations specified in both parameters must succeed.

If the value of this parameter is less than the number of enabled, valid MANDATORY destinations, this parameter is ignored in favor of the MANDATORY destination count. If the value is more than the number of enabled, valid MANDATORY destinations, some of the enabled, valid OPTIONAL non-standby destinations are treated as MANDATORY.

You can switch dynamically from using the older parameters to the LOG_ARCHIVE_DEST_n parameter using ALTER SYSTEM, as follows:

Set LOG_ARCHIVE_MIN_SUCCEED_DEST to 1.

Set the value of LOG_ARCHIVE_DEST and LOG_ARCHIVE_DUPLEX_DEST to the null string.

Set the desired number of destinations for the LOG_ARCHIVE_DEST_n parameters.

Reset LOG_ARCHIVE_MIN_SUCCEED_DEST to the desired value.