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.

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This column is obsolete and maintained for backward compatibility.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 an Oracle Real Application Clusters (Oracle RAC) environment. In a non-Oracle 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

CON_DBID

NUMBER

The database ID of the PDB for the sampled session

CON_ID

NUMBER

The ID of the container that CON_DBID identifies. Possible values include:

• 0: This value is used for rows containing data that pertain to the entire CDB. This value is also used for rows in non-CDBs.

• 1: This value is used for rows containing data that pertain to only the root

• n: Where n is the applicable container ID for the rows containing data