"Null Line" in a PRINT SPACE report

Products

• IDMS
• IDMS - Database

Issue/Introduction

Running the PRINT SPACE utility on an area, it reports under the record type column statistics for a record named "Null Line". For example:

             Maximum                                          Percent of
Record Type  Length       Occurrences   Total Space Used      Total Used
 
Null Line         8          1,012               3,264             0.00

What does a record type of "Null Line" mean in a PRINT SPACE report? Does it indicate a problem?

Environment

Release: All supported releases.

Resolution

Each record stored in a database page has a pointer in the page footer called a line index, which identifies its location in the page and its record type. The "Null Line" in the record type refers to a line index that was previously used by a database record but has since been erased. When a record is erased and the line index is in the middle of other line indexes, it is overwritten with binary zeroes. This null line index can be reused by the next record that is stored in the database page. The existence of null line indexes is normal and does not indicate a problem with the database. Running an UNLOAD/RELOAD will clean up these null line indexes.