SQL/MX Glossary

Glossary

HP NonStop SQL/MX Glossary—523732-002

Glossary-40

user metadata tables

user metadata tables. For SQL/MX, these metadata tables reside in user schemas. The

HISTOGRAM and HISTOGRAM_INTERVALS tables contain histogram statistics for

user tables within a database. One set of these tables resides in each user schema.

The SYSTEM_DEFAULTS table contains default settings for query execution options.

There is one SYSTEM_DEFAULTS table on each node where SQL/MX is installed.

There are additional user metadata tables, MVS_TABLE_INFO_UMD, MVS_UMD, and

MVS_USED_UMD, that are currently unused but reside in each user schema. For

SQL/MP objects referenced by SQL/MX, these are SQL/MP tables, called HISTOGRM

and HISTINTS, created by SQL/MX that contain histogram statistics for SQL/MP

tables. See also definitional integrity, host identifier, and MPALIAS table.

utility. A software tool that can be used to perform a specialized task. SQL/MX utilities can

be command -line driven, such as Import/Export, ImportDDL/ExportDDL, and

Cleanup/Verify; syntaxed-based, such as MODIFY, DUP, and PURGEDATA; or API-

based, such as NSM/web, and Backup/Restore.

versioning. To enable different versions of software to interoperate across nodes and

releases. Database versioning allows the software to determine if the version of a

particular object is compatible. Query plan versioning allows the software to assign a

version to query plans and modules, and determine if that version is compatible.

view. A table that has a logical definition and a file label but contains no data. A view is

derived by projecting a subset of the columns, restricting a subset of the rows, or both,

from one or more base tables or other views.

visibility. The ability to see a database object from a node if a catalog reference for that

object’s catalog exists on that node.

Visual Query Planner. An SQL/MX application that enables you to extract and display

query execution plans generated by the optimizer for DML statements. Visual Query

Planner connects to an SQL/MX database by using ODBC/MX and queries the result

table of the EXPLAIN function, as applied to a DML statement, to extract query plan

information.

volume recovery. The automatic process of recovering database files to their most recent

consistent state if they become inconsistent because of a disk volume or system

failure. To recover files, the volume recovery process redoes committed transactions to

ensure that they are reflected correctly in the database, and then backs out all

transactions that were incomplete at the time of the interruption.

wild-card character. A character that matches any other character or set of characters in a

fileset, predicate, or command.