The DATERTNX parameter controls the value placed in the Found Code for a Fetch by Count operation using Date Sensitive Processing.
With a Fetch by Count operation it is possible that the row retrieved is not within the date range. When this occurs, the Found Code should be set to N to reflect the logical condition that the retrieved row is not a match.
When Date Sensitive Processing was first introduced as a user contributed program, the Found Code returned under this condition was X. The default setting of N for DATERTNX ensures that this release operates as before and will return an X. If your applications do not require this backwards compatibility, it is strongly recommended that you set DATERTNX to Y so that the found code will be N when this condition occurs.