Subfiles can be specified in the DDS for a display-device file to allow you to handle multiple records of the same type on the display. (See Figure 193.) A subfile is a group of records that is read from or written to a display-device file. For example, a program reads records from a database file and creates a subfile of output records. When the entire subfile has been written, the program sends the entire subfile to the display device in one write operation. The work-station user can change data or enter additional data in the subfile. The program then reads the entire subfile from the display device into the program and processes each record in the subfile individually.
Records that you want to be included in a subfile are specified in the DDS for the file. The number of records that can be included in a subfile must also be specified in the DDS. One file can contain more than one subfile, and up to 12 subfiles can be active concurrently. Two subfiles can be displayed at the same time.
The DDS for a subfile consists of two record formats: a subfile-record format and a subfile control-record format. The subfile-record format contains the field information that is transferred to or from the display file under control of the subfile control-record format. The subfile control-record format causes the physical read, write, or control operations of a subfile to take place. Figure 194 shows an example of the DDS for a subfile-record format, and Figure 195 shows an example of the DDS for a subfile control-record format.
For a description of how to use subfile keywords, 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/..
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To use a subfile for a display device file in an RPG program, you must specify the SFILE keyword on a file description specification for the WORKSTN file. The format of the SFILE keyword is SFILE(record format name:RECNO field name). The WORKSTN file must be an externally-described file (E in position 22).
You must specify for the SFILE keyword the name of the subfile record format (not the control-record format) and the name of the field that contains the relative record number to be used in processing the subfile.
In an RPG program, relative record number processing is defined as part of the SFILE definition. The SFILE definition implies a full-procedural update file with ADD for the subfile. Therefore, the file operations that are valid for the subfile are not dependent on the definition of the main WORKSTN file. That is, the WORKSTN file can be defined as a primary file or a full-procedural file.
Use the CHAIN, READC, UPDATE, or WRITE operation codes with the subfile record format to transfer data between the program and the subfile. Use the READ, WRITE, or EXFMT operation codes with the subfile control-record format to transfer data between the program and the display device or to process subfile control operations.
Subfile processing follows the rules for relative-record-number processing. The RPG program places the relative-record number of any record retrieved by a READC operation into the field named in the second position of the SFILE keyword. This field is also used to specify the record number that the RPG program uses for WRITE operation to the subfile or for output operations that use ADD. The RECNO field name specified for the SFILE keyword must be defined as numeric with zero decimal positions. The field must have enough positions to contain the largest record number for the file. (See the SFLSIZ keyword in 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/.) The WRITE operation code and the ADD specification on the output specifications require that a relative-record-number field be specified in the second position of the SFILE keyword on the file description specification.
If a WORKSTN file has an associated subfile, all implicit input operations and explicit calculation operations that refer to the file name are processed against the main WORKSTN file. Any operations that specify a record format name that is not designated as a subfile are processed on the main WORKSTN file.
If you press a specified function key during a read of a non-subfile record, subsequent reads of a subfile record will cause the corresponding function key indicator to be set on again, even if the function key indicator has been set off between the reads. This will continue until a non-subfile record is read from the WORKSTN file.
*.. 1 ...+... 2 ...+... 3 ...+... 4 ...+... 5 ...+... 6 ...+... 7 ..*
AAN01N02N03T.Name++++++RLen++TDpBLinPosFunctions++++++++++++++++++++*
A** CUSTOMER NAME SEARCH
A REF(DSTREF) 1
A R SUBFIL SFL 2
A TEXT('Subfile Record')
A CUST R 7 3
A NAME R 7 10
A ADDR R 7 32 3
A CITY R 7 54
A STATE R 7 77
A*The data description specifications (DDS) for a subfile record format describe the records in the subfile: