ORA-600 2252 错误与SCN的一致性

当数据库系统的时间被调整，回到历史状态时，数据库可能出现ORA-600 2252错误。

这个错误指，数据库的SCN被认为是错误和不合理的，Oracle内部控制每秒产生的SCN数量小于 16K 个，然后以1988年1月1日，0点0分0秒开始，可以计算出一个SCN可能的合理最大值。

如果当前SCN的指标超过了这个合理值，则系统就会出现ORA-600 2252错误。
这类错误的错误号可能类似如下：

Mon May 14 17:55:54 2012
Errors in file /t3/orat3/product/admin/ora1020410/bdump/ora1020410_mmon_25386.trc:
ORA-00600: internal error code, arguments: [2252], [2988], [9], [], [], [], [], []
Mon May 14 17:56:06 2012
Errors in file /t3/orat3/product/admin/ora1020410/bdump/ora1020410_smon_23805.trc:
ORA-00600: internal error code, arguments: [2252], [2988], [13], [], [], [], [], []
Mon May 14 17:56:06 2012
Non-fatal internal error happenned while SMON was doing extent coalescing.
SMON encountered 1 out of maximum 100 non-fatal internal errors.
Mon May 14 17:56:07 2012
Errors in file /t3/orat3/product/admin/ora1020410/bdump/ora1020410_smon_23805.trc:
ORA-00600: internal error code, arguments: [2252], [2988], [13], [], [], [], [], []
Non-fatal internal error happenned while SMON was doing extent coalescing.
SMON encountered 2 out of maximum 100 non-fatal internal errors.
Mon May 14 17:56:09 2012
Errors in file /t3/orat3/product/admin/ora1020410/bdump/ora1020410_smon_23805.trc:
ORA-00600: internal error code, arguments: [2252], [2988], [14], [], [], [], [], []
Non-fatal internal error happenned while SMON was doing extent coalescing.
SMON encountered 3 out of maximum 100 non-fatal internal errors.
Mon May 14 17:56:10 2012
Errors in file /t3/orat3/product/admin/ora1020410/bdump/ora1020410_smon_23805.trc:
ORA-00600: internal error code, arguments: [2252], [2988], [14], [], [], [], [], []
Non-fatal internal error happenned while SMON was doing extent coalescing.
SMON encountered 4 out of maximum 100 non-fatal internal errors.
Mon May 14 17:56:11 2012
Errors in file /t3/orat3/product/admin/ora1020410/bdump/ora1020410_smon_23805.trc:
ORA-00600: internal error code, arguments: [2252], [2988], [15], [], [], [], [], []
Non-fatal internal error happenned while SMON was doing extent coalescing.
SMON encountered 5 out of maximum 100 non-fatal internal errors.

如果确实因为调整系统时间导致，则可以将时间调整回正确日期，如果系统SCN真的非法跃迁，则可以等候一定时间，等候SCN合理值可以容纳该跃迁或不一致。