IBM 000-8697 Instrukcja Użytkownika Pobierz pdf (Strona 219)

100

101

System Architecture 2-125

Data Pages and Data Row Storage

Eventually, a row may outgrow its original storage location. If this occurs, a

forward pointer to the new location of the data row is left at the position

deﬁned by the rowid. The forward pointer is itself a rowid that deﬁnes the

page and the location on the page where the data row is now stored. (Refer

to page 2-127 forfurtherinformation abouttheroleof the forward pointer in

row storage.)

Data Pages and Data Row Storage

The variable length of a data row has consequences for row storage:

■ A page may contain one or more whole rows.

■ A page may contain portions of one or more rows.

■ A page may contain a combination of whole rows and partial rows.

■ An updated row may increase insize andbecome too long to return

to its original storage location in a row.

The following paragraphs describe the guidelines OnLine follows during

datastorage. Refer topage 2-121forfurther information abouttheroleofthe

slot table in data storage. Refer to page 2-123 for further information about

the role of the rowid in data storage.

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