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Static Cluster Screen
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This screen provides information about the clustering of indexes and referential constraints in a DBEFileSet.

[cluster]

To invoke the Static Cluster screen, use the c command from the Static subsystem or the /st c command from other subsystems.

Field Definitions

DBEFILESET

The name of the DBEFileSet.

The keyword DETACHED means that the DBEFileSet is detached. The keywords DETACHED DBEFILES mean that the DBEFileSet is attached, but some of the DBEFiles within it are detached.

OWNER.TABLE

The name of each table in the DBEFileSet that has an index or referential constraint defined upon it. Indexes and referential constraints are listed below the table name, and are preceded by the following labels:

(INDEX)

A nonclustering index, created by using the CREATE INDEX statement or by specifying a unique constraint.

(INDEX*)

A clustering index, created by using the CREATE CLUSTERING INDEX statement or by specifying a unique constraint with the CLUSTERING ON CONSTRAINT clause in the CREATE TABLE statement.

(CONST)

A nonclustering PCR (parent-child relationship), created by defining a referential constraint.

(CONST*)

A clustering PCR (parent-child relationship), created by defining a referential constraint with the CLUSTERING ON CONSTRAINT clause in the CREATE TABLE statement.

TABLE PAGES

The number of pages containing data for the table.

TOTAL ROWS

The total number of rows in the table.

UNLOAD/LOAD SUGGESTED %

The percentage of rows in the table that are not physically stored in index order, calculated as follows:

  ( (CCOUNT - TABLE PAGES) / (TOTAL ROWS - TABLE PAGES) ) * 100

When the index is well clustered, CCOUNT equals TABLE PAGES, and the percentage is equal to zero. As the clustering of the index degrades, CCOUNT approaches TOTAL ROWS, and the percentage increases.

Performance is best when CCOUNT is equal to TABLE PAGES. As CCOUNT approaches TOTAL ROWS, performance degrades. When the percentage is high, additional I/O is required to perform an index scan over the table. To improve performance, UNLOAD the data in sorted order and LOAD it back in again with ISQL.

CCOUNT

The total number of pages touched when a complete scan of the table is made in index order. CCOUNT is incremented each time the next row to be accessed is on a different page than the previous row. If the data is not physically stored in index order, the same page is touched more than once.

Display Conventions

The full bright, inverse video bars represent a value of 100%. The actual percentage is indicated by the half bright, inverse video bars, which are delimited on the right with exclamation points.

Related SET Commands

Use the SET DBEFILESET command to improve performance and display only those tables contained in a particular DBEFileSet.



Static Screen
  		 


Static DBEFile Screen