Corporation Switch User Manual

Agile 9.2.2.1
I received an ORA-01555 error. What should I do?
ORA-01555: "snapshot too old (rollback segment too small" when using Automatic Undo Management
(AUM).
Solution: The UNDO tablespace is too small. Increase the size of the UNDO tablespace. Note
that the UNDO tablespace should be large enough to store the undo data generated by active
transactions as well as those preserved to honor the undo retention setting.
Increase the value of the Undo_retention parameter. This is important for systems running long
queries. The parameter’s value should at least be equal to the length of the longest running
query on a given database instance. This can be determined by querying the V$UNDOSTAT
view once the database has been running for a while:
SQL> select max (maxquerylen) from v$undostat;
How long does it take the AUT to run?
The amount of time it takes the AUT to run depends on the database size. The amount of time
needed to upgrade is also based on the database version of the source database. Import and
export steps can be avoided by using the sourceEqualsDest property which also reduces the
time.
Page - 24 Database Upgrade Guide