For every request in OIM, OIM User Interface allows justification of 4000 characters but if you provide justification of 4000 characters, you will see error in the SOA Logs:
ORA-12899: value too large for column "
_SOAINFRA"."WFMESSAGEATTRIBUTE"."STRINGVALUE" (actual: 4000, maximum: 2000)
which means SOA supports justification of maximum of 2000 characters.
Put a solution in OIM UI (can be done in many ways) to restrict users from entering justification of more than 2000 characters.