![](https://pdfstore-manualsonline.prod.a.ki/pdfasset/d/64/d64eda7c-5f30-498e-91c7-80e21a9f0c47/d64eda7c-5f30-498e-91c7-80e21a9f0c47-bgd9.png)
System Architecture 2-123
Data Row Format and Rowid
Data Row Format and Rowid
OnLine can store rows that are longer than a page. OnLine also supports the
VARCHAR data type, which results in rows of varying length.
As a result, rows do not conform to a single format. The following facts about
rows must be considered when OnLine stores data rows in a page:
■ Rows within a table are not necessarily the same length.
■ The length of a row may change when it is modified.
■ The length of a row can be greater than a page.
■ Blobs are not stored within the data row. Instead, the data row
contains a 56-byte descriptor that points to the location of the blob.
(The descriptor can point to either a dbspace blob page or a
blobspace blobpage.)
Refer to IBM Informix Guide to SQL: Tutorial for instructions about how to
estimate the length of fixed-length and variable-length data rows.
The term rowid refers to a unique 4-byte integer that is a combination of a
page identification number (the logical page number) and the number of an
entry in the slot table on that page. The rowid defines the location of a data
row. (Refer to page 2-121 for a definition of the slot table and how it stores the
location of a data row on a page.) The page that contains the first byte of the
data row is the page that is specified by the rowid. This page is called the data
row home page.