Direct update mode

The update mode is direct.

Whenever possible, Adaptive Server uses direct update mode, since it is faster and generates fewer log records than deferred update mode.

The direct update mode operates as follows:

Pages are read into the data cache.
The changes are recorded in the transaction log.
The change is made to the data page.
The transaction log page is flushed to disk when the transaction commits.

For more information on the different types of direct updates, see “How Update Operations Are Performed” on page 112.

Adaptive Server uses direct update mode for the following delete command:

delete 
from authors 
where au_lname = "Willis" 
and au_fname = "Max"

QUERY PLAN FOR STATEMENT 1 (at line 1).

    STEP 1
        The type of query is DELETE.
        The update mode is direct.

        FROM TABLE
            authors
        Nested iteration.
        Using Clustered Index.
        Index : au_names_ix
        Forward scan.
        Positioning by key.
        Keys are:
            au_lname  ASC
            au_fname  ASC
        Using I/O Size 2 Kbytes for index leaf pages.
        With LRU Buffer Replacement Strategy for index leaf pages.
        Using I/O Size 2 Kbytes for data pages.
        With LRU Buffer Replacement Strategy for data pages.
        TO TABLE
            authors