NonStop SQL/MP Reference Manual

Table Of Contents
NonStop SQL/MP Reference Manual142115
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Considerations—AUDITCOMPRESS
Compressed audit records omit unchanged columns from the before and after images of
updated rows. Uncompressed audit records allow you to read complete rows in the audit
trail but require more space.
Considerations—AUDITCOMPRESS
Benefits of AUDITCOMPRESS
AUDITCOMPRESS can save system resources, so you should allow tables and
indexes to default to AUDITCOMPRESS, unless you have a specific requirement to
read audit trail files with complete before and after images.
Difference between compressed and uncompressed row images
Audit records of uncompressed files contain entire before and after images of
changed rows. Audit records of compressed files generally contain only changed
columns and columns of the primary key. Other columns are occasionally included
to improve performance, such as when a single unchanged column physically occurs
between several changed columns.
Reading audit trails from programs
Programs can read audit trails written with or without audit compression by using
TMF audit-reading procedures.
AUDITCOMPRESS and the CREATE INDEX...WITH SHARED ACCESS
operation
If AUDITCOMPRESS is on at the start of a CREATE INDEX operation that uses
the WITH SHARED ACCESS option, NonStop SQL/MP turns AUDITCOMPRESS
off. When finished with the CREATE INDEX operation, SQL turns
AUDITCOMPRESS back on. If the CREATE INDEX operation fails, however,
SQL might leave the AUDITCOMPRESS attribute off. You can use the ALTER
TABLE statement to turn the attribute back on.
Audited Tables
Audited tables are tables audited by TMF (Transaction Management Facility). TMF
monitors all transactions against audited tables in preparation for possible transaction
backout or NonStop TM/MP recovery operations.
NonStop SQL/MP creates audited tables by default, but you can specify the creation of a
nonaudited table (or change an audited table to a nonaudited table) with the AUDIT file
attribute for the table.
All NonStop SQL/MP catalog tables are audited. In addition, SQL tables must reside on
audited volumes, even if the tables themselves are not audited.
{ AUDITCOMPRESS | NO AUDITCOMPRESS }
The table default is AUDITCOMPRESS.
The index default is the table value at index creation.