oracle init parameters

db_file_multiblock_read_count

• Segment headers ard read with single-block reads
• Physical reads never span server extents.
• Blocks already in the buffer cache, except for direct read, are not reread from I/O subsystem.

If the initialization parameter db_file_multiblock_read_count is set to 8, the following
physical reads are performed:
• One single-block read of the segment header (block 1).
• One multiblock read of two blocks (2 and 3). More blocks cannot be read because block 4
is cached.
• One multiblock read of four blocks (from 5 to 8). More blocks cannot be read because
block 9 is cached.
• One multiblock read of six blocks (from 11 to 16). More blocks cannot be read because
block 16 is the last one of the extent.
• One multiblock read of two blocks (17 and 18). More blocks cannot be read because
block 19 is cached.
• One single-block read of block 20. More blocks cannot be read because block 21 is cached.
• One multiblock read of eight blocks (from 22 to 29). More blocks cannot be read because
the initialization parameter db_file_multiblock_read_count is set to 8.
• One multiblock read of three blocks (from 30 to 32).