默认情况下,SCN多长时间递增一次呢，今天同事突然讨论这个问题，数据库版本如下：
SQL> select * from v$version;
SQL> select dbms_flashback.get_system_change_number from dual;
GET_SYSTEM_CHANGE_NUMBER
------------------------
1544192
采用scn_to_timestamp获取scn与时间的对应关系如下：
SQL> select scn_to_timestamp(&scn) from dual;
Enter value for scn: 1544192
old 1: select scn_to_timestamp(&scn) from dual
new 1: select scn_to_timestamp(1544192) from dual
SCN_TO_TIMESTAMP(1544192)
---------------------------------------------------------------------------
28-MAR-12 05.18.36.000000000 PM
将scn递增一次检查时间如下：
SQL> /
Enter value for scn: 1544193
old 1: select scn_to_timestamp(&scn) from dual
new 1: select scn_to_timestamp(1544193) from dual
SCN_TO_TIMESTAMP(1544193)
---------------------------------------------------------------------------
28-MAR-12 05.18.39.000000000 PM
如上可见2个时间差为3秒，
可见时间差仍然没变。