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Oracle® Database Reference 10g Release 2 (10.2) Part Number B14237-02 |
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# DBA_HIST_INSTANCE_RECOVERY

`DBA_HIST_INSTANCE_RECOVERY` displays the historical monitoring of the mechanisms available to the user to limit recovery I/O. This view contains snapshots of `V$INSTANCE_RECOVERY`.

Column | Datatype | NULL | Description
--- | --- | --- | ---
`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`FAST_START_IO_TARGET_REDO_BLKS` | `NUMBER` |  | This column is obsolete and maintained for backward compatibility.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 (RAC) 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