ORA-1555

production database throw ORA-1555 error. but my undo tablespace size is bigger than my user tableapce.

details:

Current Undo Configuration

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Current undo tablespace : UNDOTBS1

Current undo tablespace size (datafile size now) : 28322M

Current undo tablespace size (consider autoextend) : 32768M

AUTOEXTEND for undo tablespace is : ON

Current undo retention : 3600

UNDO GUARANTEE is set to : TRUE

SQL>Select fs.tablespace_name "Tablespace", (df.totalspace - fs.freespace) "Used MB", fs.freespace "Free MB", df.totalspace "Total MB",

round(100 * (fs.freespace / df.totalspace)) "Pct. Free" from(select tablespace_name,round(sum(bytes) / 1048576) TotalSpace from

dba_data_files group by tablespace_name) df,(select tablespace_name, round(sum(bytes) / 1048576) FreeSpace from