V$INSTANCE_RECOVERY

V$INSTANCE_RECOVERY

V$INSTANCE_RECOVERY monitors the mechanisms available to users to limit recovery I/O. Those mechanisms are:

Set the LOG_CHECKPOINT_TIMEOUT initialization parameter
Set the LOG_CHECKPOINT_INTERVAL initialization parameter
Set the FAST_START_MTTR_TARGET initialization parameter
Set the size of the smallest redo log

Column	Datatype	Description
`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 that parameter 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 that parameter 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`FAST_START_IO_TARGET_REDO_BLKS`	`NUMBER`	This column is obsolete and maintained for backward compatibility.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), 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, 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). Basically, this value tells you how long you could expect recovery to take based on the work your 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 the user configure all online redo logs to be at least this value.
`ESTD_CLUSTER_AVAILABLE_TIME`	`NUMBER`	Estimated time (in seconds) that the cluster would become partially available should this 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` initialization 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 or LOG_CHECKPOINT_TIMEOUT` initialization parameter
`WRITES_OTHER_SETTINGS`	`NUMBER`	Number of writes driven by other reasons (such as the deprecated `FAST_START_IO_TARGET` initialization 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

See Also:

Oracle Database Performance Tuning Guide for more information on limiting recovery I/O, and how Oracle determines MTTR recovery times
LOG_CHECKPOINT_INTERVAL
FAST_START_MTTR_TARGET