Oracle Waits event:DB File Scattered Read
The DB File Scattered Read wait event generally indicates waits related to
full table scans or fast
full index scans. As full table scans are pulled
into memory, they are scattered throughout the
buffer cache, since it is
usually unlikely that they fall into contiguous buffers. A large number
indicates that there may be missing or suppressed indexes. This could also
be preferred, since it
may be more efficient to perform. a full table scan
than an index scan. Check to ensure full table
scans are necessary when you
see these waits. Try to cache small tables to avoid reading them
into memory
over and over again. Locate the data on disk systems that have either more disk
caching or are buffered by the OS file system cache.
DB_FILE_MULTIBLOCK_READ_COUNT
can make full scans faster (but it could also
influence Oracle to do more of them). You can also
partition tables and
indexes so that only a portion is scanned. Slow File I/O (slow disks) can
cause these waits. Correlated to each of the waits are the values for
P1,P2,P3=file, block, blocks.
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