While hashing may seem rather dull at this point, this section will clearly demonstrate why two syntactically exact SQL statements are treated as two distinct and different SQL statements! If you have every wondered why select * from dual is considered different from select * from Dual, read on!

Before a library cache object is associated with a bucket, it must be hashed. If you look closely at each library cache object shown in Figure 7-6, you'll see each has a hash value. Oracle creates this hash value based on its own proprietary algorithm. Once the hash value is generated, it is then entered into Oracle's proprietary library cache hashing algorithm, which results in the bucket number.

The library cache object hashing situation is more complicated than with block hashing. We're not dealing with a file number and a block number. This situation requires hashing the object's text. So if a SQL statement or a package is 2,000 lines long, Oracle may choose to hash all this text.