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v$db_cache_advice:

The predictive models for Oracle RAM areas began with the v$db_cache_advice utility in Oracle9i. 

The v$db_cache_advice  view is similar to an Oracle7 utility that also predict the benefit of adding data buffers. 

The Oracle7 utility used the x$kcbrbh view to track buffer hits and the x$kcbcbh view to track buffer misses. 

The utility is the foundation of the Oracle10g Automatic Memory Management (AMM) utility that monitors and adjusts the sizes of the Oracle data buffers

Oracle9i r2 advisory utilities:

The advisory utilities are extremely important for the Oracle DBA who must adjust the sizes of the RAM areas to meet current processing demands. Oracle9i r2 supports three advisory utilities

PGA advice:

v$pga_target_advice is a new advisory utility introduced by Oracle 9i .  

v$pga_target_advice utility will show the marginal changes in optimal, one-pass, and multipass PGA execution for different sizes of pga_aggregate_target , ranging from 10% to 200% of the current value.

Shared Pool advice:

The shared Pool advisory functionality has been extended in Oracle9i release 2 to include a new advice called v$shared_pool_advice , and there is talk to expending the advice facility to all SGA RAM areas in future releases of Oracle.

Data Cache advice:

The v$db_cache_advice utility show the marginal changes in physical data block reads for different sizes of db_cache_size .

The data XE "data buffer hit ratio" from STATSPACK can provide similar data as v$db_cache_advice, and most Oracle tuning professionals use STATSPACK and v$db_cache_advice to monitor the effectiveness of their data buffers.

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