If the normal search method for a copybook has failed, then with this option turned on CP will retry with the name specified in the source converted to uppercase. If still no match is found, then it will try a further time with the name converted to lower-case. The name will be tried with the full usual search methodology. Note that the case conversion affects precisely what is specified in the source, so will include paths and extensions if specified there; however, it will not affect COBCPY paths or COPYEXT directive values, where the specified case will always be preserved.