CACHE | NOCACHE | CACHE READS

Use the CACHE clauses to indicate how Oracle Database should store blocks in the 
buffer cache. If you specify neither CACHE nor NOCACHE, then:

In a CREATE TABLE statement, NOCACHE is the default

In an ALTER TABLE statement, the existing value is not changed.

CACHE

For data that is accessed frequently, this clause indicates that the 
blocks retrieved for this table are placed at the most recently used 
end of the least recently used (LRU) list in the buffer cache when a
 full table scan is performed. This attribute is useful for small lookup tables.

As a parameter in the LOB_storage_clause, CACHE specifies that the
 database places LOB data values in the buffer cache for faster access.

Restriction on CACHE

You cannot specify CACHE for an index-organized table. However,
 index-organized tables implicitly provide CACHE behavior.

NOCACHE

For data that is not accessed frequently, this clause indicates that
 the blocks retrieved for this table are placed at the least recently
 used end of the LRU list in the buffer cache when a full table scan 
is performed. NOCACHE is the default for LOB storage.

As a parameter in the LOB_storage_clause, NOCACHE specifies 
that the LOB value either is not brought into the buffer cache or
 is brought into the buffer cache and placed at the least recently 
used end of the LRU list. The latter is the default behavior.

Restriction on NOCACHE

You cannot specify NOCACHE for an index-organized table.

CACHE READS

CACHE READS applies only to LOB storage. It specifies that LOB 
values are brought into the buffer cache only during read operations
 but not during write operations.
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