Space Management › Area Space Management › SR1 Records

SR1 Records

Each database page in an area contains an SR1 record in the page header. Each occurrence of the SR1 record contains the space available count for that page. The SR1 record type is the owner of a set used by CA IDMS/DB to keep track of CALC records (for details, see "Storing CALC records" in Chapter 36, “Record Storage and Deletion”).

SR1 Record Format

The SR1 record is formatted as follows:

• Next pointer for CALC set (4 bytes)—Database key (next pointer) of the CALC record, targeted to that page, with the lowest CALC key
• Prior pointer for CALC set (4 bytes)—Database key (prior pointer) of the CALC record, targeted to that page, with the highest CALC key
• Space available count (2 bytes)—Number of bytes of free space remaining on the page
• Filler (2 bytes)—Reserved space

Line Index

Every line index 0 in an area identifies the location of an SR1 record and always contains the following values:

• record identification = 1
• displacement = 4
• record length = 12
• prefix length = 8

The following diagram shows an empty page in an area. This is what a page would look like after initialization by the FORMAT utility.

Note: The space available count for an empty page is always the page size minus 32 (in this case, 800 - 32 = 768) and the line space count for an empty page is always 16. The CALC set pointers in the SR1 record on an empty page point back to the SR1 record itself since it is the only record in the set.