The following high-level tuning indicators can be used to establish if a database is performing optimally or not:
. Buffer Cache Hit Ratio
Formula: Hit Ratio = (Logical Reads - Physical Reads) / Logical Reads
Action: Increase DB_CACHE_SIZE (DB_BLOCK_BUFFERS prior to 9i) to increase hit ratio
. Library Cache Hit Ratio
Action: Increase the SHARED_POOL_SIZE to increase hit ratio