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Variable Mandatory value
DB2_SKIPDELETED ON
Allows index-range queries or table-scan queries to skip
records that are in an uncommitted delete state. This
reduces the amount of lock contention from Read Share
and Next Key Share locks from range queries in tables
with a high frequency of deletes.
When enabled, DB2_SKIPDELETED allows, where
possible, table or index access scans to defer or avoid
row locking until a data record is known to satisfy
predicate evaluation. This allows predicate evaluation
to occur on uncommitted data.
This variable is applicable only to statements using
either Cursor Stability or Read Stability isolation levels.
For index scans, the index must be a type-2 index.
Deleted rows are skipped unconditionally on table scan
access while deleted keys are not skipped for type-2
index scans unless DB2_SKIPDELETED is also set.
Recommended value: ON
DB2_SKIPINSERTED ON
Allows SELECTs with Cursor Stability or Read Stability
isolation levels to skip uncommitted inserted rows. This
reduces record lock contention on tables with heavy
insert rates.
Recommended settings for IBM DB2 registry variables
IBM DB2 registry values include recommended settings for IBM DB2 performance
with Sterling B2B Integrator.
Variable Recommended value
DB2_USE_ALTERNATE_
PAGE_CLEANING
ON
DB2_
EVALUNCOMMITTED
ON
Enabling this variable can reduce the amount of
unnecessary lock contention from Read Share and Next
Key Share. By default, DB2 requests share locks on the
index or record before verifying if the record satisfies
the query predicate. Queries that scan a set of records
in tables with high frequency of inserts or updates can
unnecessarily block records that do not belong to its
result set.
When you set DB2_EVALUNCOMMITTED to ON, DB2
performs an uncommitted read on the record to
perform the predicate verification. If the record satisfies
the predicate, DB2 requests a share lock on that record.
36 Sterling B2B Integrator: Performance Management