SQL/MP Reference Manual

HP NonStop SQL/MP Reference Manual—523352-013
S-57
Similarity Between Collations
Tables referenced in the position of tablea in this statement can be similar, but
tables referenced in the position of tableb in this statements can never be
similar:
SELECT columnx FROM tablea
WHERE EXISTS SELECT [DISTINCT] * FROM tableb;
SELECT tableb.*, tablea.x FROM tableb, tablea;
Similarity Between Collations
Collations that are explicitly referenced in an SQL query are similar only if they are
equal. SQL uses the procedure CPRL_COMPAREOBJECTS_ to determine
equivalence of collations.
Displaying the Similarity Check Attribute
Information on the similarity check for a table can be retrieved from the catalog where
the table is registered. To display this information, enter This SQLCI query:
Select tablename,similaritycheck from catalog.tables
where tablename like "% TABLENAME%";
TABLENAME must be uppercase.
SLACK File Attribute
SLACK is a file attribute that specifies the minimum percentage of space to leave for
future insertions when loading data and index blocks. SLACK applies only to
key-sequenced files and to indexes.
percent
is an integer from 0 to 99 that specifies the percent of empty space to leave in
each data and index block during loading.
The default is 15 percent.
Purpose of SLACK

SLACK specifications are usually between 15 and 25 percent.

Specifying a larger than normal SLACK value when a file is initially loaded and
many more inserts are expected can improve performance by reducing the number
of block splits required when inserts occur.

For a file expected to have little activity, you can save disk space by specifying a
smaller than normal SLACK value.
SLACK percent