Oracle Database Administration: The Essential Refe

Initialization Parameters

These INIT.ORA parameters determine how the cost-based optimizer will perform; see Chapter 12, for valid values and defaults.

ALWAYS_ANTI_JOIN

Sets the type of antijoin that the Oracle Server uses. The system checks to verify that it is legal to perform an antijoin; if it is, the system processes the subquery depending on the value of this parameter. When set to the value NESTED_LOOPS, the Oracle Server uses a nested loop antijoin algorithm. When set to the value MERGE, the Oracle Server uses the sort merge antijoin algorithm. When set to the value HASH, the Oracle Server uses the hash antijoin algorithm to evaluate the subquery.

B_TREE_BITMAP_PLANS

Allows the optimizer to use bitmap index plans even though a table only has B-Tree indexes.

BITMAP_MERGE_AREA_SIZE

Specifies the amount of memory used to merge bitmaps retrieved from a range scan of the index. A larger value should improve performance because the bitmap segments must be sorted before being merged into a single bitmap.

COMPLEX_VIEW_MERGING

Determines whether complex views and subqueries are evaluated on their own or are merged into the entire query for evaluation.

DB_FILE_MULTIBLOCK_READ_COUNT

Specifies the maximum number of blocks read in one I/O operation during a sequential scan. The total number of I/Os needed to perform a full table scan depends on factors such as the size of the table, the value of MULTI_BLOCK_READ_COUNT, and whether Parallel Query is being utilized for the operation. Batch environments ...