SNAP_ID |
NUMBER |
NOT NULL |
Unique snapshot ID |
DBID |
NUMBER |
NOT NULL |
Database ID for the snapshot |
INSTANCE_NUMBER |
NUMBER |
NOT NULL |
Instance number for the snapshot |
RECOVERY_ESTIMATED_IOS |
NUMBER |
|
Number of dirty buffers in the buffer cache. In the Standard Edition, this column is always null. |
ACTUAL_REDO_BLKS |
NUMBER |
|
Current actual number of redo blocks required for recovery |
TARGET_REDO_BLKS |
NUMBER |
|
Current target number of redo blocks that must be processed for recovery. This value is the minimum value of the following 3 columns, and identifies which of the 3 user-defined limits determines checkpointing. |
LOG_FILE_SIZE_REDO_BLKS |
NUMBER |
|
Maximum number of redo blocks required to guarantee that a log switch does not occur before the checkpoint completes |
LOG_CHKPT_TIMEOUT_REDO_BLKS |
NUMBER |
|
Number of redo blocks that need to be processed during recovery to satisfy the LOG_CHECKPOINT_TIMEOUT parameter. The value displayed is not meaningful unless LOG_CHECKPOINT_TIMEOUT has been set. |
LOG_CHKPT_INTERVAL_REDO_BLKS |
NUMBER |
|
Number of redo blocks that need to be processed during recovery to satisfy the LOG_CHECKPOINT_INTERVAL parameter. The value displayed is not meaningful unless LOG_CHECKPOINT_INTERVAL has been set. |
FAST_START_IO_TARGET_REDO_BLKS |
NUMBER |
|
This column is obsolete and maintained for backward compatibility. The value of this column is always null. |
TARGET_MTTR |
NUMBER |
|
Effective MTTR (mean time to recover) target value in seconds. The TARGET_MTTR value is calculated based on the value of the FAST_START_MTTR_TARGET parameter (the TARGET_MTTR value is used internally), and is usually an approximation of the parameter's value. However, if the FAST_START_MTTR_TARGET parameter value is very small (for example, one second), or very large (for example, 3600 seconds), then the calculation will produce a target value dictated by system limitations.
In such cases, the TARGET_MTTR value will be the shortest calculated time, or the longest calculated time that recovery is expected to take. If FAST_START_MTTR_TARGET is not specified, then the value of this field is the current estimated MTTR. |
ESTIMATED_MTTR |
NUMBER |
|
Current estimated mean time to recover (MTTR) based on the number of dirty buffers and log blocks (0 if FAST_START_MTTR_TARGET is not specified). This value tells you how long you can expect recovery to take based on the work the system is doing right now. |
CKPT_BLOCK_WRITES |
NUMBER |
|
Number of blocks written by checkpoint writes |
OPTIMAL_LOGFILE_SIZE |
NUMBER |
|
Redo log file size (in megabytes) that is considered optimal based on the current setting of FAST_START_MTTR_TARGET. It is recommended that all online redo logs be configured to be at least this value. |
ESTD_CLUSTER_AVAILABLE_TIME |
NUMBER |
|
Estimated time (in seconds) that the cluster would become partially available should the instance fail. This column is only meaningful in a Real Application Clusters environment. In a non-RAC environment, the value of this column is null. |
WRITES_MTTR |
NUMBER |
|
Number of writes driven by the FAST_START_MTTR_TARGET parameter |
WRITES_LOGFILE_SIZE |
NUMBER |
|
Number of writes driven by the smallest redo log file size |
WRITES_LOG_CHECKPOINT_SETTINGS |
NUMBER |
|
Number of writes driven by the LOG_CHECKPOINT_INTERVAL parameter or the LOG_CHECKPOINT_TIMEOUT parameter |
WRITES_OTHER_SETTINGS |
NUMBER |
|
Number of writes driven by other reasons (such as the deprecated FAST_START_IO_TARGET parameter) |
WRITES_AUTOTUNE |
NUMBER |
|
Number of writes due to auto-tune checkpointing |
WRITES_FULL_THREAD_CKPT |
NUMBER |
|
Number of writes due to full thread checkpoints |
