I want to change my redo log buffer or database buffer cache size. Kindly tell me what the algorithm is to change the size.
For the redo log buffer, if your database is experiencing a high degree of waits for space in the log buffer, consider increasing the size, but remember that it is almost never necessary for the size of a redo log buffer to exceed several hundred kilobytes.
For the buffer cache, make use of the buffer cache sizing advice embodied in the V$DB_CACHE_ADVICE data dictionary table, either via your own queries or the Enterprise Manager interface to this information. Each row in this view shows the estimated I/O activity for a given cache size; you can thus see how much more (or less) disk reads would be required for various cache sizes.