To hasten the input operations required for a data set on DASD, the operating system uses a technique called search direct in its channel programs. Search direct reads in the requested record and the count field of the next record. This lets the operation get the next record directly, along with the count field of the record that follows it. Search direct (OPTCD=Z) is an obsolete DCB macro and DD statement option. Now the system generally uses this technique for sequential reading.

When sharing data sets, you must consider the restrictions of search direct. Search direct can cause unpredictable results when multiple DCBs are open and the data sets are being shared, and one of the applications is adding records. You might get the wrong record. Also, you might receive unpredictable results if your application has a dependency that is incompatible with the use of search direct.