ORA-32766

Error: ORA-32766: instr with negative offset: use varchar semantics on LOBs

Causa: The current varchar behavior is different. That is, instr('abcd', 'cd', -2, 1) returns 3, whereas instr(to_clob('abcd'), 'cd', -2, 1) returns 0, (for example, no match), because the reverse search starts from offset -2, which points to 'c' and moving backward, 'd' is ignored. This is symmetric to instr('dcba','dc',2,1), which returns 0.

Acción: ORACLE uses the same varchar semantics on LOBs (instr). Using the same example, instr(to_clob('abcd'), 'cd', -2, 1) will return 3 as in the varchar case.