Init parameterOptimizer & SQL

DB_FILE_MULTIBLOCK_READ_COUNT

What it controls

Blocks read in one I/O during full scans.

Know this before you change it

Leave it unset. Oracle then uses the largest efficient I/O size and costs plans on realistic numbers.

Check and change it

1-- Current value on every instance2SELECT inst_id, name, value, isdefault, ismodified3FROM gv$parameter4WHERE name = 'db_file_multiblock_read_count';5 6-- Value stored in the spfile7SELECT sid, value FROM v$spparameter WHERE name = 'db_file_multiblock_read_count' AND isspecified = 'TRUE';8 9-- Dynamic: takes effect now and is kept after a restart10ALTER SYSTEM SET db_file_multiblock_read_count = 128 SCOPE = BOTH SID = '*';11 12-- Or for your own session only13ALTER SESSION SET db_file_multiblock_read_count = 128;14 15-- Remove it from the spfile to go back to the default at the next restart16ALTER SYSTEM RESET db_file_multiblock_read_count SCOPE = SPFILE SID = '*';

Open in the parameter referenceOracle's reference

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