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SQL programmingYou can use the HCL OneDB™ implementation of the SQL language to develop applications for HCL OneDB™ database servers.
Guide to SQL: SyntaxThe HCL OneDB™ Guide to SQL: Syntax describes the syntax of the statements, data types, expressions, operators, and built-in functions of the HCL OneDB™ dialect of the SQL language.
SQL statementsThis chapter describes the syntax and semantics of SQL statements that are recognized by HCL OneDB™.
UPDATE STATISTICS statementUse the UPDATE STATISTICS statement to update system catalog information that the query optimizer uses for operations on objects in the local database. The UPDATE STATISTICS statement is an extension to the ANSI/ISO standard for SQL.
Updating Statistics for TablesAlthough a change to the database might make information in the systables, syscolumns, sysindices, sysfragments, sysdistrib, and sysfragdist system catalog tables obsolete, the database server does not automatically update those tables after most SQL statements.
Examining Index Pages

Examining Index Pages

In HCL OneDB™, when you execute the UPDATE STATISTICS statement in any mode, the database server reads through index pages to:

Compute statistics for the query optimizer
Locate pages that have the delete flag marked as 1

If pages are found with the delete flag marked as 1, the corresponding keys are removed from the B-tree cleaner list.

This operation is particularly useful if a system failure causes the B-tree cleaner list (which exists in shared memory) to be lost. To remove the B-tree items that have been marked as deleted but are not yet removed from the B-tree, run the UPDATE STATISTICS statement. For information on the B-tree cleaner list, see your HCL OneDB Administrator's Guide.

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