Oracle Error Codes

maximum key length (string) exceeded

The combined length of all the columns specified in a CREATE INDEX statement exceeded the maximum index length. The maximum index length varies by operating system. The total index length is computed as the sum of the width of all indexed columns plus the number of indexed columns. Date fields have a length of 7, character fields have their defined length, and numeric fields have a length of 22. Numeric length = (precision/2) + 1. If negative, add +1.

How to Solve :

Select columns to be indexed so the total index length does not exceed the maximum index length for the operating system. See also your operating system-specific Oracle documentation.