HISAM and SHISAM database

HISAM and SHISAM databases share the following record formats.

Segment Format

Figure 1 and Figure 2 show the segment format of HISAM and SHISAM.

Figure 1. HISAM segment format
Graphic shows HISAM segment format. A 4 column, 1 row table is shown. The first column (from left to right) is labeled "SEG. CODE" and is 1 byte. The second column is labeled "DEL. FLAG" and is 1 byte. The third column is labeled "LP PTR OR COUNTER OR LC POINTERS" and has "optional" for its byte length. Also, the third column references note 1 below. The fourth column is labeled "DATA." Columns 1 through 3 are designated as "PREFIX" columns. Column 4, is designated as a "DATA" column.

Note:

1.
This field can be omitted, or it can be used to hold:
  • A 4-byte LP pointer (if this segment is an LC).
  • A 4-byte counter (if this segment is an LP).
  • One or more 4-byte LC pointers (if this segment is an LP).
Figure 2. SHISAM segment format
Graphic is the words "NO PREFIX" in parenthesis, followed by a rectangular box labeled "DATA."
Note: This diagram is for a root-only database.
LRECL Format
The following figure shows the LRECL format.
Figure 3. LRECL format
Graphic shows a 6 column, 1 row table. Column 1 is labeled "POINTER" and has a reference to note 1 below. Column 2 is labeled "SEGMENT" and has a reference to note 2 below. Column 3 is labeled "SEGMENT." Column 3 also indicates that it is a field that repeats any specified number of times until column 4. Column 4 is labeled "ZERO" and has a reference to note 3 below. Column 5 is labeled "POINTER OR ZERO" and has a reference to note 4 below. Column 6 is labeled "RESIDUAL" and has a reference to note 5 below. Also, underneath column 6 there is an arrow pointing away to the right, referencing note 6 below.
Notes:
1.
4-byte RBA of ESDS record containing additional dependent segments for this root occurrence.

SHISAM: This field is omitted.

2.
HISAM: Segment includes prefix and data.

SHISAM: Segment includes only data (no prefix). (See Figure 2)

3.
1-byte of zeros indicates the end of segments in this LRECL.
4.
This field is omitted.
5.
Space not used.
6.
VSAM LRECLs must have an even length.
VSAM Block Formats

The following figure shows the VSAM block formats.

Figure 4. VSAM block formats
Graphic shows a 4 column, 1 row table. The table is labeled "VSAM." Column 1 (from left to right) is labeled "LRECL" and references note 1 below. Columns 2 and 3 are also labeled "LRECL." Column 4 is labeled "CONTROL INFO." and references note 2 below.
Notes:
1.
LRECL length might change between KSDS and ESDS, depending on user definition.
2.
10 bytes in a blocked data set; 7 bytes in an unblocked data set.