I have a table with 70,000 rows and one of the columns is CLOB data type. When I try to select * from that table I get the following error:
ERROR: ORA-01555: snapshot too old: rollback segment number with name "" too small
ORA-22924: snapshot too old
The database is Oracle9i release 1 and I am using undo tablespace.
You get the ORA-1555 message when you try to access data that someone else is modifying, and Oracle has lost the information that it needs to construct a read-consistent image of that data to present to you. Since you are using Oracle9i's new UNDO tablespace, the ORA-1555 error is an indication that your UNDO_RETENTION parameter is not large enough. You can monitor this by querying the SSOLDERRCNT (Snap Shot Too Old Error Count) column of V$UNDOSTAT. Increase the UNDO_RETENTION parameter and these errors will go away.
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