现象：
solaris 系统oracle 9i单实例数据库
SQL> alter system switch logfile; ###hang住了
解决方法：
1、生成10046文件：
SQL> select value from v$parameter where name = 'user_dump_dest';
VALUE
--------------------------------------------------------------------------------
/ora/szuat/szuatdb/9.2.0/admin/SZPRD_mis-uat/udump
SQL> alter session set events '10046 trace name context forever ,level 8';
Session altered
SQL> alter system switch logfile;
^C alter system switch logfile
*
ERROR at line 1:
ORA-01013: user requested cancel of current operation
SQL> alter session set events '10046 trace name context off' ;
Session altered.
2、查看等待事件：
WAIT #1: nam='switch logfile command' ela= 866 p1=0 p2=0 p3=0
WAIT #1: nam='switch logfile command' ela= 439 p1=0 p2=0 p3=0
WAIT #1: nam='switch logfile command' ela= 484 p1=0 p2=0 p3=0
WAIT #1: nam='switch logfile command' ela= 544 p1=0 p2=0 p3=0
WAIT #1: nam='switch logfile command' ela= 781 p1=0 p2=0 p3=0
WAIT #1: nam='switch logfile command' ela= 576 p1=0 p2=0 p3=0
WAIT #1: nam='switch logfile command' ela= 337 p1=0 p2=0 p3=0
WAIT #1: nam='switch logfile command' ela= 383 p1=0 p2=0 p3=0
3、修改参数：
SQL> show parameter log_archive_start
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
log_archive_start boolean FALSE
SQL> alter system archive log start; ##alter system set log_archive_start=true scope=spfile;
System altered.
4、问题恢复：
SQL> alter system switch logfile;
System altered.
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