Item | Description | Evaluation |
|---|---|---|
Buffer cache hit rate | The role of buffer caches is to reduce the number of accesses to the disk (data files). | Increase the value of the initialization parameter "DB_BLOCK_BUFFERS" or "DB_CACHE_SIZE" that specifies the size of the buffer cache. Note: - "DB_CACHE_SIZE" is a new initialization parameter that was added in Oracle9i. - Pay attention to the remaining physical memory capacity. |
REDO log buffer cache | The REDO log buffer cache stores the information that is written to the online REDO log. | If processing to write to the REDO log buffer cache enters a wait state, increase the value of the initialization parameter "LOG_BUFFERS". If I/O processing performed from the REDO log buffer cache to a disk enters a wait state, move the REDO log file to a dedicated disk or a high-speed RAID device. If the REDO log file is located on the file system, consider using direct I/O or moving to a raw device. If Oracle8 or earlier is being used and latch waiting occurs to the REDO log buffer cache, decrease the value of the initialization parameter "LOG_SMALL_ENTRY_MAX_SIZE". If the above tuning is not effective, increase the value of the initialization parameter "LOG_SIMULTANEOUS_COPIES". |
Library cache hit rate | The library cache stores the SQL statements that have been analyzed and can be executed. | Increase the value of the initialization parameter "SHARED_POOL_SIZE". Pay attention to the remaining physical memory capacity. |
Dictionary cache hit rate | The dictionary cache stores data dictionary information such as the status of file space for database segments (indexes, sequence, tables, etc.) and object permissions. | Increase the value of the initialization parameter "SHARED_POOL_SIZE". Pay attention to the remaining physical memory capacity. |
