NonStop SQL/MP Reference Manual

NonStop SQL/MP Reference Manual—142115
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ICOMPRESS File Attribute
ICOMPRESS is a file attribute that controls key compression in index blocks.
ICOMPRESS applies only to key-sequenced tables and to indexes.
The table default is NO ICOMPRESS.
The index default is the table value at index creation.
Considerations—ICOMPRESS
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Purpose of ICOMPRESS
Occasionally, the use of ICOMPRESS can reduce the number of index levels.
Reducing the number of index levels improves performance.
You can check the number of index levels by looking at the INDEXLEVELS
column of the INDEXES catalog table. (ALTER INDEX does not update the
INDEXLEVELS column but UPDATE STATISTICS does.) If ICOMPRESS does
not reduce index levels, it lowers performance but saves disk space.
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How indexes are compressed
The disk process does a sequential scan of all indexes in the block, beginning at the
start of the block. This function is similar to DCOMPRESS; savings result when the
index contains many like values.
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Relative and entry-sequenced tables
Relative and entry-sequenced tables always have the NO ICOMPRESS attribute, but
index block compression has no meaning for them.
IF/THEN/ELSE Clause
IF/THEN/ELSE is an SQLCI report writer clause that specifies a condition for printing
one or the other of two print lists. It works in the BREAK FOOTING, BREAK TITLE,
DETAIL, PAGE FOOTING, PAGE TITLE, REPORT FOOTING, and REPORT TITLE
commands.
You can nest IF/THEN/ELSE clauses.
cond-expr
is a conditional expression that determines whether the THEN clause or the ELSE
clause contains the list to print.
{ ICOMPRESS | NO ICOMPRESS }
IF cond-expr THEN (print-list) [ ELSE (print-list) ]