SQL - SYSIBM.SYSSTATFEEDBACK - www.cadcobol.com.br


Volta ao Menu das SYSIBM

Volta ao Menu Principal


Desenvolvido por DORNELLES, Carlos Alberto - Analista de Sistemas - Brasília DF. - cad_cobol@hotmail.com

SYSIBM.SYSSTATFEEDBACK
Db2 for z/OS 12.0.0

A tabela SYSTATFEEDBACK contém informações sobre estatísticas de catálogo ausentes ou conflitantes para instruções SQL.
O esquema é SYSIBM.

Os valores a seguir controlam a coleta de dados de feedback de estatísticas na tabela do catálogo SYSSTATFEEDBACK:

  • O parâmetro do subsistema STATFDBK_SCOPE controla se os dados são coletados e se são coletados apenas para instruções SQL estáticas, apenas para instruções SQL dinâmicas ou para ambos.
  • O parâmetro do subsistema STATSINT controla quando e com que frequência os dados são externalizados.
  • A coluna STATS_FEEDBACK da tabela do catálogo SYSTABLES controla se os dados são coletados para uma tabela específica.

O utilitário RUNSTATS remove dados da tabela do catálogo SYSSTATFEEDBACK quando as estatísticas recomendadas são coletadas.

Dica:
A tabela SYSSTATFEEDBACK pode conter linhas que recomendam a coleta de estatísticas para objetos DEFINE NO ou partições de espaço de tabela vazio.
No entanto, as estatísticas não podem ser coletadas para esses objetos até que os dados sejam inseridos e os conjuntos de dados subjacentes sejam criados.

The SYSTATFEEDBACK table contains information about missing or conflicting catalog statistics for SQL statements.
The schema is SYSIBM.

The following values control the collection of statistics feedback data in the SYSSTATFEEDBACK catalog table:
  • The STATFDBK_SCOPE subsystem parameter controls whether the data is collected, and whether it is collected only for static SQL statements, only for dynamic SQL statements, or for both.
  • The STATSINT subsystem parameter controls when and how frequently the data is externalized.
  • The STATS_FEEDBACK column of the SYSTABLES catalog table controls whether the data is collected for a particular table.

The RUNSTATS utility removes data from the SYSSTATFEEDBACK catalog table when the recommended statistics are collected.

Tip:
The SYSSTATFEEDBACK table might contain rows that recommend collection of statistics for DEFINE NO objects, or empty table space partitions.
However, statistics cannot be collected for such objects until after data is inserted and the underlying data sets are created.

Column name Data type Description Use
TBCREATOR VARCHAR(128) The creator of the table. S
TBNAME VARCHAR(128) The name of the table. S
IXCREATOR VARCHAR(128) The creator of the index. S
IXNAME VARCHAR(128) The name of the index. S
COLNAME VARCHAR(128) The name of the column. S
NUMCOLUMNS SMALLINT The number of columns in the column group. S
COLGROUPCOLNO VARCHAR(254) FOR BIT DATA A hex representation that identifies the set of columns associated with the statistics.
If the statistics are only associated with a single column, the field contains a zero length.
Otherwise, the field is an array of SMALLINT column numbers with a dimension equal to the value in NUMCOLUMNS. 		S
TYPE CHAR(1) The type of statistic to collect:
'C'
Cardinality.
'F'
Frequency.
'H'
Histogram.
'I'
Index.
'T'
Table.
 I
DBNAME VARCHAR(24) The name of the database. S
TSNAME VARCHAR(24) The name of the table space. S
REASON CHAR(8) The reason for the statistics collection recommendation:
'BASIC'
A basic statistical value for a column table or index is missing.
'CONFLICT'
Another statistic conflicts with this statistic.
'COMPFFIX'
Multi-column cardinality statistics are needed for an index compound filter factor.
'DEFAULT'
A predicate references a value that is probably a default value.
'KEYCARD'
The cardinalities of index key columns are missing.
'LOWCARD'
The cardinality of the column is a low value, which indicates that data skew is likely.
'NULLABLE'
Distribution statistics are not available for a nullable column.
'RANGEPRD'
Histogram statistics are not available for a range predicate.
'PARALLEL'
Parallelism could be improved by uniform partitioning of key ranges.
'STALE'
A statistic appears likely to be out of sync with other statistics, based on comparison of the time that it was collected to statistics collection times for related objects.
 S
BLOCK_RUNSTATS CHAR(1) Whether the row is used when optimization tools collect statistics based on the recommendations.
Db2 inserts a blank value in this column for all new rows.
Db2 does not refer to or change the value of this column.
This is an updatable column.		 S
REMARKS VARCHAR(254) Free form text for extensibility. S
LASTDATE DATE The last date that this statistics recommendation was updated by Db2. S

© Copyright IBM Corp.