For the sequential-by-key method of processing, records are read from the file in key sequence.
The sequential-by-key method of processing is valid for keyed files used as primary, secondary, or full procedural files.
For output files and for input files that do not use random functions (such as SETLL, SETGT, CHAIN, or ADD) and that have only one record format, the ILE RPG compiler defaults to or operates as though SEQONLY(*YES) had been specified on the CL command OVRDBF. (The ILE RPG compiler does not operate as though SEQONLY(*YES) had been specified for update files.) SEQONLY(*YES) allows multiple records to be placed in internal data management buffers; the records are then passed to the ILE RPG compiler one at a time on input.
If, in the same job, two files use the same physical file, and one file is processed sequentially and one is processed for random update, a record could be updated that has already been placed in the buffer that is presented to the program. In this case, when the record is processed from the sequential file, the record does not reflect the updated data. To prevent this problem, use the CL command OVRDBF and specify the option SEQONLY(*NO), which indicates that you do not want multiple records transferred for a sequentially processed file.
For more information on sequential only processing, refer to the DB2 Universal Database for iSeries section of the Database and File Systems category in the i5/OS Information Center at this Web site - http://www.ibm.com/systems/i/infocenter/.