Trailing blank compression

Blanks at the end of segments are compressed if all of the following are true.

Specifying COMPR

You can specify trailing blank compression (COMPR=) as FIXED, SHORT, or ALL.

FIXED

If COMPR=FIXED is specified, MFS removes trailing blanks from fixed-length data fields. The resulting mapping in the DFLD is as if the application program inserted a short data field (by inserting X'3F' in the position after significant data or by inserting a short segment) or omitted the field (by inserting X'3F' in the first position of the field or by inserting a short segment) if the entire field contains blanks.

Fields shortened by an application program are not compressed in the same way as when COMPR=FIXED is specified. This option is provided for application programs that always supply maximum-length fields (such as the NAME field) for simplicity of the application program, and these blanks are not significant to the receiver. The receiver can assume that fields shortened or omitted by the compress option or by the application program have the same meaning.

SHORT

If COMPR=SHORT is specified, MFS removes trailing blanks from the data fields shortened by the application program. The resulting mapping in the DFLD is as if the application program inserted a short field with no trailing blanks or omitted the field. Fixed-length fields do not undergo this compression.

This option is provided for application programs written for the 3270 and without application program changes.

ALL

If COMPR=ALL is specified, the trailing blanks in the fixed-length and short fields are removed.

Trailing blanks in a short field or a single blank short field causes a specific operation on the 3270 (that is, to clear the entire field on the screen for a single blank and insert a program tab character (FILL=PT), or to clear the remaining portion of the updated field and insert one or more null characters (FILL=NULL)).

Saving line transmission time

Line transmission time can be saved by using one of the following methods:

  • Specifying COMPR=ALL, which removes the trailing blanks in fixed-length and short fields
  • Defining record mode, and defining the fields as occurring at the end of the record

Blank compression on variable-length output

The following code example shows the data entered by the IMS application:

Segment 1: 
DLZZ  FIELD A1  | FIELD A2 |FIELD A3 |FIELD A4 |FIELDC1|FIELD C2
0200  AAAAA44444|1234563...|43.......|A4A4A4
0800       00000|      F   |0F
Segment 2: 
DLZZ  FIELD B1  | FIELD B2 |FIELD D1 |FIELD D2 |FIELD D3|FIELD E1
0300  BBBBBBBBBB|4444444444|DDDDDD43.|3........|D3D3D3D3
0400            |0000000000|      0F |F        |
Note: Both segments entered are shortened by the program.

The following table shows the MFS definitions used in the previous code example.

Table 1. MFS definitions for data entered by IMS application
MSGOUT MSG TYPE=OUTPUT, SOR=FMTOUT
  SEG  
  MFLD A1,LTH=10
  MFLD A2,LTH=10
  MFLD A3,LTH=10
  MFLD A4,LTH=10
  MFLD C1,LTH=10
  MFLD C2,LTH=10
  SEG  
  MFLD B1,LTH=10
  MFLD B2,LTH=10
  MFLD D1,LTH=10
  MFLD D2,LTH=10
  MFLD D3,LTH=10
  MFLD E1,LTH=10
  MSGEND  
FMTOUT FMT  
     

Examples of variable-length output with blank compression are shown in the code examples below.

The following code example shows variable-length output with blank compression in record mode:

VLVB    FIELD A1  THRU A4: (First record)
01      AAAAA,123456,,A4A4A4
06
VLVB    FIELD B1:          (Second record)
00      BBBBBBBBBB
0C
VLVB    NO DATA:           (Third record)
00
03
VLVB    FIELDS D1 and D3:  (Fourth record)
01        DDDDDD,,D3D3D3D3
02
Note:
  1. Field A2 was short.
  2. Field A3 had no data.
  3. Field A4 was short. Trailing separators in a record are not transmitted.
  4. Field B2 had no data.
  5. Fields C1 and C2 had no data. A 1-byte record is transmitted because more data follows.
  6. Field D1 was short.
  7. Field D2 had no data.
  8. Field E1 had no data. A record is not transmitted because no more data follows.

The following table shows the MFS definitions used for record mode output as shown in the previous code example.

Table 2. MFS definitions for record mode
Field Type Definition  
  DEV TYPE=DPM-B1, FEAT=5, MODE=RECORD  
  DIV TYPE=OUTPUT, X
    OFTAB=(c',',MIX), COMPR=ALL  
A1 DFLD LTH=10  
A2 DFLD LTH=10  
A3 DFLD LTH=10  
A4 DFLD LTH=10  
  RCD    
B1 DFLD LTH=10  
B2 DFLD LTH=10  
  RCD    
C1 DFLD LTH=10  
C2 DFLD LTH=10  
  RCD    
D1 DFLD LTH=10  
D2 DFLD LTH=10  
D3 DFLD LTH=10  
  RCD    
E1 DFLD LTH=10  
       

The following code example shows variable-length output with blank compression in stream mode:

VLVB    FIELDS A1 THROUGH D3:  (Single record)
03      AAAAA,123456,,A4A4A4,BBBBBBBBBB,,,DDDDDD,,D3D3D3D3
Note: In stream mode, a separator is not transmitted for field D3, which is short, and for field E1, which is omitted.

The following table shows the MFS definitions used for stream mode output as shown in the previous code example.

Table 3. MFS definitions for stream mode
Field Type Definition  
  DEV TYPE=DPM-B1, FEAT=6, MODE=STREAM  
  DIV TYPE=OUTPUT, X
    OFTAB=(c',',MIX), COMPR=ALL  
A1 DFLD LTH=10  
A2 DFLD LTH=10  
A3 DFLD LTH=10  
A4 DFLD LTH=10  
B1 DFLD LTH=10  
B2 DFLD LTH=10  
C1 DFLD LTH=10  
C2 DFLD LTH=10  
D1 DFLD LTH=10  
D2 DFLD LTH=10  
D3 DFLD LTH=10  
E1 DFLD LTH=10  
  FMTEND