ORA-31408: invalid value specified for begin_scn or end_scn
Cause: The begin_scn was not greater than zero. The end_scn was less than zero. The end_scn was less than the begin_scn.
Action: Check the values of both begin_scn and end_scn. Correct them to make sure that they form a legal SCN range. An end_scn value of zero indicates an infinite scn range.
ORA-31408错误表示传递给外部表的值无效，该值是指BEGIN_SCN或END_SCN中的值。
ORA-31408: invalid value specified for begin_scn or end_scn
Cause: A value was specified that is invalid for either a begin_scn or end_scn parameter.
Action: Ensure that the value specified is valid, and corresponds to an existing SCN.
ORA-31408通常发生在当程序尝试使用表中的SCN值填充BEGIN_SCN或END_SCN参数时，参数值无效或不存在。另外，当尝试将其他类型的数据作为SCN参数时，这种错误也会发生。
解决ORA-31408错误的正确方法是确保BEGIN_SCN或END_SCN参数的值有效，并且与表中的SCN值相符。如果这条错误消息出现在程序中，请检查程序的实现，确保参数被正确设置。如果参数值不存在，请将其分配给表中的有效值。确保表中有一个有效的SCN值，应当可以解决这个问题。