Full Table Scan reads all the blocks in the table and places them in the tail end of the LRU list, if the table is defined with NOCACHE option. Those cached data blocks may be flushed out very soon when Oracle finds no space in the SGA for the new blocks from another query.

Full Table Scan reads all the blocks in the table and places them in the beginning of the LRU list, if the table is defined with CACHE option.