Error: ORA 1460
Text: unimplemented or unreasonable conversion requested
-------------------------------------------------------------------------------
Cause: The requested format conversion is not supported.
Action: Remove the requested conversion from the SQL statement.
Check the syntax for the TO_CHAR, TO_DATE, and TO_NUMBER functions to
see which conversions are supported.

*** Important: The notes below are for experienced users - See [NOTE:22080.1]


Diagnosis:
Isolate which types are being converted between.

NB: This can occur in OCI applications if bind NUMBER types to native
integer types when the LENGTH / Max Length fields are incorrect
for the allowable native integer types. Eg: len=3 is invalid on
most platforms.
.



For more information check the oracle metalink

Sam