基于rac环境下的参数变更小测

alter system switchlogfile;---只能独立在每个rac实例运行，没有所谓的全局或单实例的说法

请参考如下测试

SQL> alter system switch logfile;---先后运行switch logfile两次，很简单，不再引述

System altered.
SQL> select * from gv$log  ---rac默认每个实例内建四组redo,每个实例分为两个不同的thread
  2  ;

   INST_ID     GROUP#    THREAD#  SEQUENCE#      BYTES    MEMBERS ARC STATUS           FIRST_CHANGE# FIRST_TIM
---------- ---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- ---------
         2          1          1          2   52428800          1 YES INACTIVE                493667 12-APR-10
                    2          1          3   52428800          1 NO  CURRENT                 500152 12-APR-10
                    3          2          3   52428800          1 NO  CURRENT                 500449 12-APR-10
                    4          2          2   52428800          1 YES ACTIVE                  490928 12-APR-10
         1          1          1          2   52428800          1 YES INACTIVE                493667 12-APR-10
                    2          1          3   52428800          1 NO  CURRENT                 500152 12-APR-10
                    3          2          3   52428800          1 NO  CURRENT                 500449 12-APR-10
                    4          2          2   52428800          1 YES ACTIVE                  490928 12-APR-10

8 rows selected.



运行这个语句alter system archive log instance 'only1' current，可以限制归档实例的范围，对哪个实例进行归档操作

具体测试如下：
1,未运行以上语句前
SQL> select * from gv$log;


   INST_ID     GROUP#    THREAD#  SEQUENCE#      BYTES    MEMBERS ARC STATUS           FIRST_CHANGE# FIRST_TIM
---------- ---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- ---------
         1          1          1          2   52428800          1 YES INACTIVE                493667 12-APR-10   
                    2          1          3   52428800          1 NO  CURRENT                 500152 12-APR-10    ---请注意看status为current这列与下面第四行（这是当前日志）
                    3          2          3   52428800          1 NO  CURRENT                 500449 12-APR-10
                    4          2          2   52428800          1 YES INACTIVE                490928 12-APR-10
         2          1          1          2   52428800          1 YES INACTIVE                493667 12-APR-10
                    2          1          3   52428800          1 NO  CURRENT                 500152 12-APR-10
                    3          2          3   52428800          1 NO  CURRENT                 500449 12-APR-10
                    4          2          2   52428800          1 YES INACTIVE                490928 12-APR-10

8 rows selected.



2，运行以上语名
SQL> alter system archive log instance 'only1' current;---对rac实例1(only1)进行归档

System altered.


3,再次查看gv$log
SQL> select * from gv$log;

   INST_ID     GROUP#    THREAD#  SEQUENCE#      BYTES    MEMBERS ARC STATUS           FIRST_CHANGE# FIRST_TIM
---------- ---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- ---------
         1          1          1          4   52428800          1 NO  CURRENT                 500789 12-APR-10
                    2          1          3   52428800          1 YES ACTIVE                  500152 12-APR-10    ---看到了没，此日志已经归档了，arc列为yes(第四行同样）
                    3          2          3   52428800          1 NO  CURRENT                 500449 12-APR-10
                    4          2          2   52428800          1 YES INACTIVE                490928 12-APR-10
         2          1          1          4   52428800          1 NO  CURRENT                 500789 12-APR-10
                    2          1          3   52428800          1 YES ACTIVE                  500152 12-APR-10
                    3          2          3   52428800          1 NO  CURRENT                 500449 12-APR-10
                    4          2          2   52428800          1 YES INACTIVE                490928 12-APR-10

8 rows selected.

SQL>



小结：
  rac架构不同于单实例数据库,故有些参数可以独立定制；当然有些参数必须是全局统一的