6.3.1.3 Monitoring Exadata Smart Flash Cache Using Exadata Metrics

Exadata metrics that are related to Exadata Smart Flash Cache are identified in the Exadata storage server METRICCURRENT, METRICDEFINITION, and METRICHISTORY objects as having objectType=FLASHCACHE.

Example 6-1 Displaying Flash Cache Metric Definitions

This example shows how to display the flash cache metric definitions that are available in the Oracle Exadata System Software.

CellCLI> LIST METRICDEFINITION ATTRIBUTES NAME,DESCRIPTION WHERE OBJECTTYPE = FLASHCACHE
         FC_BYKEEP_DIRTY                         "Number of megabytes unflushed for keep objects on FlashCache"
         FC_BYKEEP_OLTP                          "Number of megabytes for OLTP keep objects in flash cache"
         FC_BYKEEP_OVERWR                        "Number of megabytes pushed out of the FlashCache because of space limit for keep objects"
         FC_BYKEEP_OVERWR_SEC                    "Number of megabytes per second pushed out of the FlashCache because of space limit for keep objects"
         FC_BYKEEP_USED                          "Number of megabytes used for keep objects on FlashCache"
         FC_BY_ALLOCATED                         "Number of megabytes allocated in flash cache"
         FC_BY_ALLOCATED_DIRTY                   "Number of megabytes allocated for unflushed data in flash cache"
         FC_BY_ALLOCATED_OLTP                    "Number of megabytes allocated for OLTP data in flash cache"
         FC_BY_DIRTY                             "Number of unflushed megabytes in FlashCache"
         FC_BY_STALE_DIRTY                       "Number of unflushed megabytes in FlashCache which cannot be flushed because cached disks are not accessible"
         FC_BY_USED                              "Number of megabytes used on FlashCache"
         FC_COL_BYKEEP_USED                      "Number of megabytes used for keep objects in Columnar FlashCache"
         FC_COL_BY_USED                          "Number of megabytes used in Columnar FlashCache"
         FC_COL_IO_BYKEEP_R                      "Number of megabytes read from Columnar FlashCache for keep objects"
         FC_COL_IO_BYKEEP_R_SEC                  "Number of megabytes read per second from Columnar FlashCache for keep objects"
         FC_COL_IO_BY_R                          "Number of megabytes that were read from Columnar FlashCache"
         FC_COL_IO_BY_R_ELIGIBLE                 "Number of megabytes eligible to read from Columnar FlashCache"
         FC_COL_IO_BY_R_ELIGIBLE_SEC             "Number of megabytes per second eligible to read from Columnar FlashCache"
         FC_COL_IO_BY_R_SEC                      "Number of megabytes per second that were read from Columnar FlashCache"
         FC_COL_IO_BY_SAVED                      "Number of megabytes saved by reads from Columnar FlashCache"
         FC_COL_IO_BY_SAVED_SEC                  "Number of megabytes saved per second by reads from Columnar FlashCache"
         FC_COL_IO_BY_W_POPULATE                 "Number of megabytes that are population writes into Columnar FlashCache due to read miss"
         FC_COL_IO_BY_W_POPULATE_SEC             "Number of megabytes per second that are population writes into Columnar FlashCache due to read miss"
         FC_COL_IO_RQKEEP_R                      "Number of requests read for keep objects from Columnar FlashCache"
         FC_COL_IO_RQKEEP_R_SEC                  "Number of requests read per second for keep objects from Columnar FlashCache"
         FC_COL_IO_RQ_R                          "Number of requests that were read from Columnar FlashCache"
         FC_COL_IO_RQ_R_ELIGIBLE                 "Number of reads eligible for Columnar FlashCache"
         FC_COL_IO_RQ_R_ELIGIBLE_SEC             "Number of reads per second eligible for Columnar FlashCache"
         FC_COL_IO_RQ_R_SEC                      "Number of requests per second that were read from Columnar FlashCache"
         FC_COL_IO_RQ_W_POPULATE                 "Number of requests that are population writes into Columnar FlashCache due to read miss"
         FC_COL_IO_RQ_W_POPULATE_SEC             "Number of requests per second that are population writes into Columnar FlashCache due to read miss"
         FC_IO_BYKEEP_R                          "Number of megabytes read from FlashCache for keep objects"
         FC_IO_BYKEEP_R_SEC                      "Number of megabytes read per second from FlashCache for keep objects"
         FC_IO_BYKEEP_W                          "Number of megabytes written to FlashCache for keep objects"
         FC_IO_BYKEEP_W_SEC                      "Number of megabytes per second written to FlashCache for keep objects"
         FC_IO_BY_DISK_WRITE                     "Number of megabytes written from flash cache to hard disks"
         FC_IO_BY_DISK_WRITE_SEC                 "Number of megabytes per second written from flash cache to hard disks"
         FC_IO_BY_R                              "Number of megabytes of small reads (OLTP) from flash cache"
         FC_IO_BY_R_ACTIVE_SECONDARY             "Number of megabytes for active secondary reads satisfied from flash cache"
         FC_IO_BY_R_ACTIVE_SECONDARY_MISS        "Number of megabytes for active secondary reads not satisfied from flash cache"
         FC_IO_BY_R_ACTIVE_SECONDARY_MISS_SEC    "Number of megabytes per second for active secondary reads not satisfied from flash cache"
         FC_IO_BY_R_ACTIVE_SECONDARY_SEC         "Number of megabytes per second for active secondary reads satisfied from flash cache"
         FC_IO_BY_R_DISK_WRITER                  "Number of megabytes read from flash cache by disk writer"
         FC_IO_BY_R_DISK_WRITER_SEC              "Number of megabytes per second read from flash cache by disk writer"
         FC_IO_BY_R_DW                           "Number of megabytes of large reads (DW) from flash cache"
         FC_IO_BY_R_DW_SEC                       "Number of megabytes of large reads (DW) per second from flash cache"
         FC_IO_BY_R_MISS                         "Number of megabytes of small reads (OLTP) from disks because some of the requested data was not in flash cache"
         FC_IO_BY_R_MISS_DW                      "Number of megabytes of large reads (DW) from disks because some of the requested data was not in flash cache"
         FC_IO_BY_R_MISS_DW_SEC                  "Number of megabytes of large reads (DW) per second from disks because some of the requested data was not in flash cache"
         FC_IO_BY_R_MISS_SEC                     "Number of megabytes of small reads (OLTP) per second from disks because some of the requested data was not in flash cache"
         FC_IO_BY_R_SEC                          "Number of megabytes of small reads (OLTP) per second from flash cache"
         FC_IO_BY_R_SKIP                         "Number of megabytes read from disks for IO requests that bypass FlashCache"
         FC_IO_BY_R_SKIP_FC_THROTTLE             "Number of megabytes read from disk for IO requests that bypass FlashCache due to heavy load on FlashCache"
         FC_IO_BY_R_SKIP_FC_THROTTLE_SEC         "Number of megabytes read per second from disk for IO requests that bypass FlashCache due to heavy load on FlashCache"
         FC_IO_BY_R_SKIP_LG                      "Number of megabytes read from disk for IO requests that bypass FlashCache due to the large IO size"
         FC_IO_BY_R_SKIP_LG_SEC                  "Number of megabytes read per second from disk for IO requests that bypass FlashCache due to the large IO size"
         FC_IO_BY_R_SKIP_NCMIRROR                "Number of megabytes read from disk for IO requests that bypass FlashCache as the IO is on non-primary, non-active secondary mirror"
         FC_IO_BY_R_SKIP_SEC                     "Number of megabytes read from disks per second for IO requests that bypass FlashCache"
         FC_IO_BY_W                              "Number of megabytes written to FlashCache"
         FC_IO_BY_W_DISK_WRITER                  "Number of megabytes written to hard disks by disk writer"
         FC_IO_BY_W_DISK_WRITER_SEC              "Number of megabytes per second written to hard disks by disk writer"
         FC_IO_BY_W_FIRST                        "Number of megabytes that are first writes into flash cache"
         FC_IO_BY_W_FIRST_SEC                    "Number of megabytes per second that are first writes into flash cache"
         FC_IO_BY_W_LG_CHINT                     "Number of megabytes used for large writes to flash cache due to cache hint"
         FC_IO_BY_W_LG_DTAGE                     "Number of megabytes used for data aging large writes to flash cache"
         FC_IO_BY_W_LG_MRCV                      "Number of megabytes used for media recovery large writes to flash cache"
         FC_IO_BY_W_METADATA                     "Number of megabytes that are flash cache metadata writes"
         FC_IO_BY_W_METADATA_SEC                 "Number of megabytes per second that are flash cache metadata writes"
         FC_IO_BY_W_OVERWRITE                    "Number of megabytes that are overwrites into flash cache"
         FC_IO_BY_W_OVERWRITE_SEC                "Number of megabytes per second that are overwrites into flash cache"
         FC_IO_BY_W_POPULATE                     "Number of megabytes that are population writes into flash cache due to read miss"
         FC_IO_BY_W_POPULATE_SEC                 "Number of megabytes per second that are population writes into flash cache due to read miss"
         FC_IO_BY_W_SEC                          "Number of megabytes per second written to FlashCache"
         FC_IO_BY_W_SKIP                         "Number of megabytes written to disk for IO requests that bypass FlashCache"
         FC_IO_BY_W_SKIP_FC_THROTTLE             "Number of megabytes written to disk for IO requests that bypass FlashCache due to heavy load on FlashCache"
         FC_IO_BY_W_SKIP_FC_THROTTLE_SEC         "Number of megabytes written per second to disk for IO requests that bypass FlashCache due to heavy load on FlashCache"
         FC_IO_BY_W_SKIP_LG                      "Number of megabytes written to disk for IO requests that bypass FlashCache due to the large IO size"
         FC_IO_BY_W_SKIP_LG_SEC                  "Number of megabytes written per second to disk for IO requests that bypass FlashCache due to the large IO size"
         FC_IO_BY_W_SKIP_NCMIRROR                "Number of megabytes written to disk for IO requests that bypass FlashCache as the IO is on non-primary, non-active secondary mirror"
         FC_IO_BY_W_SKIP_SEC                     "Number of megabytes written to disk per second for IO requests that bypass FlashCache"
         FC_IO_ERRS                              "Number of IO errors on FlashCache"
         FC_IO_RQKEEP_R                          "Number of read requests for keep objects from FlashCache"
         FC_IO_RQKEEP_R_MISS                     "Number of read requests for keep objects which did not find all data in FlashCache"
         FC_IO_RQKEEP_R_MISS_SEC                 "Number of read requests per second for keep objects which did not find all data in FlashCache"
         FC_IO_RQKEEP_R_SEC                      "Number of read requests per second for keep objects from FlashCache"
         FC_IO_RQKEEP_R_SKIP                     "Number of read requests for keep objects that bypass FlashCache"
         FC_IO_RQKEEP_R_SKIP_SEC                 "Number of read requests per second for keep objects that bypass FlashCache"
         FC_IO_RQKEEP_W                          "Number of requests for keep objects which resulted in FlashCache being populated with data"
         FC_IO_RQKEEP_W_SEC                      "Number of requests per second for keep objects which resulted in FlashCache being populated with data"
         FC_IO_RQ_DISK_WRITE                     "Number of requests written from flash cache to hard disks"
         FC_IO_RQ_DISK_WRITE_SEC                 "Number of requests per second written from flash cache to hard disks"
         FC_IO_RQ_R                              "Number of small reads (OLTP) satisfied from the flash cache"
         FC_IO_RQ_REPLACEMENT_ATTEMPTED          "Number of requests attempted to find space in the flash cache"
         FC_IO_RQ_REPLACEMENT_DW_FAILED          "Number of times that client DW IOs failed to find a replacement buffer"
         FC_IO_RQ_REPLACEMENT_DW_SUCCEEDED       "Number of times that client DW IOs succeeded in finding a replacement buffer"
         FC_IO_RQ_REPLACEMENT_FAILED             "Number of requests failed to find space in the flash cache"
         FC_IO_RQ_REPLACEMENT_OLTP_FAILED        "Number of times that client OLTP IOs failed to find a replacement buffer"
         FC_IO_RQ_REPLACEMENT_OLTP_SUCCEEDED     "Number of times that client OLTP IOs succeeded in finding a replacement buffer"
         FC_IO_RQ_R_ACTIVE_SECONDARY             "Number of requests for active secondary reads satisfied from flash cache"
         FC_IO_RQ_R_ACTIVE_SECONDARY_MISS        "Number of requests for active secondary reads not satisfied from flash cache"
         FC_IO_RQ_R_ACTIVE_SECONDARY_MISS_SEC    "Number of requests per second for active secondary reads not satisfied from flash cache"
         FC_IO_RQ_R_ACTIVE_SECONDARY_SEC         "Number of requests per second for active secondary reads satisfied from flash cache"
         FC_IO_RQ_R_DISK_WRITER                  "Number of requests read from flash cache by disk writer"
         FC_IO_RQ_R_DISK_WRITER_SEC              "Number of requests per second read from flash cache by disk writer"
         FC_IO_RQ_R_DW                           "Number of large reads (DW) satisfied from the flash cache"
         FC_IO_RQ_R_DW_SEC                       "Number of large reads (DW) per second satisfied from the flash cache"
         FC_IO_RQ_R_MISS                         "Number of small reads (OLTP) that did not find all data in flash cache"
         FC_IO_RQ_R_MISS_DW                      "Number of large reads (DW) that did not find all data in flash cache"
         FC_IO_RQ_R_MISS_DW_SEC                  "Number of large reads (DW) per second that did not find all data in flash cache"
         FC_IO_RQ_R_MISS_SEC                     "Number of small reads (OLTP) per second that did not find all data in flash cache"
         FC_IO_RQ_R_SEC                          "Number of small reads (OLTP) per second satisfied from the flash cache"
         FC_IO_RQ_R_SKIP                         "Number of requests read from disk that bypass FlashCache"
         FC_IO_RQ_R_SKIP_FC_THROTTLE             "Number of requests read from disk that bypass FlashCache due to heavy load on FlashCache"
         FC_IO_RQ_R_SKIP_FC_THROTTLE_SEC         "Number of requests read from disk per second that bypassed FlashCache due to heavy load on FlashCache"
         FC_IO_RQ_R_SKIP_LG                      "Number of requests read from disk that bypass FlashCache due to the large IO size"
         FC_IO_RQ_R_SKIP_LG_SEC                  "Number of requests read from disk per second that bypass FlashCache due to the large IO size"
         FC_IO_RQ_R_SKIP_NCMIRROR                "Number of requests read from disk that bypass FlashCache as the IO is on non-primary, non-active secondary mirror"
         FC_IO_RQ_R_SKIP_SEC                     "Number of requests read from disk per second that bypass FlashCache"
         FC_IO_RQ_W                              "Number of requests which resulted in FlashCache being populated with data"
         FC_IO_RQ_W_DISK_WRITER                  "Number of requests written to hard disks by disk writer"
         FC_IO_RQ_W_DISK_WRITER_SEC              "Number of requests per second written to hard disks by disk writer"
         FC_IO_RQ_W_FIRST                        "Number of requests that are first writes into flash cache"
         FC_IO_RQ_W_FIRST_SEC                    "Number of requests per second that are first writes into flash cache"
         FC_IO_RQ_W_LG_CHINT                     "Number of large writes to flash cache due to cache hint"
         FC_IO_RQ_W_LG_DTAGE                     "Number of data aging large writes to flash cache"
         FC_IO_RQ_W_LG_MRCV                      "Number of media recovery large writes to flash cache"
         FC_IO_RQ_W_METADATA                     "Number of requests that are flash cache metadata writes"
         FC_IO_RQ_W_METADATA_SEC                 "Number of requests per second that are flash cache metadata writes"
         FC_IO_RQ_W_OVERWRITE                    "Number of requests that are overwrites into flash cache"
         FC_IO_RQ_W_OVERWRITE_SEC                "Number of requests per second that are overwrites into flash cache"
         FC_IO_RQ_W_POPULATE                     "Number of requests that are population writes into flash cache due to read miss"
         FC_IO_RQ_W_POPULATE_SEC                 "Number of requests per second that are population writes into flash cache due to read miss"
         FC_IO_RQ_W_SEC                          "Number of requests per second which resulted in FlashCache being populated with data"
         FC_IO_RQ_W_SKIP                         "Number of requests written to disk that bypass FlashCache"
         FC_IO_RQ_W_SKIP_FC_THROTTLE             "Number of requests written to disk that bypass FlashCache due to heavy load on FlashCache"
         FC_IO_RQ_W_SKIP_FC_THROTTLE_SEC         "Number of requests written to disk per second that bypass FlashCache due to heavy load on FlashCache"
         FC_IO_RQ_W_SKIP_LG                      "Number of requests written to disk that bypass FlashCache due to the large IO size"
         FC_IO_RQ_W_SKIP_LG_SEC                  "Number of requests written to disk per second that bypass FlashCache due to the large IO size"
         FC_IO_RQ_W_SKIP_NCMIRROR                "Number of requests written to disk that bypass FlashCache as the IO is on non-primary, non-active secondary mirror"
         FC_IO_RQ_W_SKIP_SEC                     "Number of requests written to disk per second that bypass FlashCache"

Note the following additional details:

• Space in Exadata Smart Flash Cache is internally managed in chunks known as cachelines. FC_BY_ALLOCATED represents the amount of space (in megabytes) that is allocated to cachelines in the flash cache. If the value is close to the flash cache size, then the flash cache is fully populated.

• FC_BY_USED represents amount of space (in megabytes) that is occupied by data in the flash cache. For some workloads, like OLTP, the FC_BY_USED value can be much less than the value of FC_BY_ALLOCATED because an OLTP write might only use a small fraction of a cacheline. The total amount used by OLTP cachelines is tracked by FC_BY_ALLOCATED_OLTP.

• Various flash cache metrics having names ending with _DW track large read operations, which are typically associated with Data Warehouse workloads. Each of these metrics has a corresponding metric that tracks small read operations, which are typically associated with OLTP operations. To get a total count, add the large read metric value to the corresponding small read metric value.

  For example, to get the total number of reads satisfied from flash cache, add FC_IO_RQ_R_DW to FC_IO_RQ_R.