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042-024

原创 Linux操作系统 作者:jbymy2000 时间:2012-03-14 12:49:22 0 删除 编辑
24.Your database is started by using the server parameter file (SPFILE). You issued this command to change the value of the LOG_BUFFER initialization parameter:
ALTER SYSTEM SET LOG_BUFFER=24M SCOPE=BOTH;
What would be the outcome of this command?
A) The command would return an error because LOG_BUFFER is a static parameter.
B) The parameter value would be changed and it would come into effect immediately.
C) You need to restart the database so that parameter changes can come into effect.
D) The command would succeed only if initialization parameter LOG_ARCHIVE_MAX_PROCESS is set to value 2.
答案:A
LOG_BUFFER是个静态参数,只能scope=spfile,修改完后重启数据库才能生效
LOG_BUFFER specifies the amount of memory (in bytes) that Oracle uses when buffering redo entries to a redo log file. Redo log entries contain a record of the changes that have been made to the database block buffers. The LGWR process writes redo log entries from the log buffer to a redo log file.
The log buffer size depends on the number of redo strands in the system. One redo strand is allocated for every 16 CPUs and has a default size of 2 MB. Oracle allocates a minimum of 2 redo strands per instance. When the log buffer size is not specified, any remaining memory in the redo granules is given to the log buffer.
LOG_BUFFER
http://download.oracle.com/docs/cd/E11882_01/server.112/e10820/initparams127.htm#REFRN10094
SQL> select name,issys_modifiable from v$parameter where name='log_buffer';
NAME ISSYS_MOD
-------------------- ---------
log_buffer FALSE
通过这个查询,我们知道,修改这个参数必须重启数据库。

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