Oracle ORA-0155 snapshot old

When a table needs to be flashed back to a long time ago, the following error is reported (the black font is a variable, which may be different each time)

ORA-0155: Snapshot old: rollback field number10(Name: "_ SYSSMU10$ ")Too small

Solution: Increase the rollback period.

Connected to Oracle Database 10g Enterprise Edition Release 10.2.0.1.0
Connected as wmis_rfid
 
SQL>Show parameter undo;
 
NAME TYPE VALUE
-----------------------------------------------------------------------------
Undo_management string AUTO
Undo_retention integer 900
Undo_tablespace string UNDOTBS1
 
SQL>Alter system set undo_retention = 10800 scope = both;
 
System altered
 
SQL> show parameter undo;
 
NAME TYPE VALUE
-----------------------------------------------------------------------------
Undo_management string AUTO
Undo_retention integer 10800
Undo_tablespace string UNDOTBS1
 
SQL>