ONDBSPACEDOWN and its effect on checkpoints

The ONDBSPACEDOWN configuration parameter specifies the response that the database server makes when an I/O error indicates that a dbspace is down. By default, the database server identifies any dbspace that contains no critical data as down and continues processing. Critical data includes the root dbspace, the logical log, or the physical log.

To restore access to that database, you must back up all logical logs and then perform a warm restore on the down dbspace.

The database server halts operation whenever a disabling I/O error occurs on a nonmirrored dbspace that contains critical data, regardless of the setting for ONDBSPACEDOWN. In such an event, you must perform a cold restore of the database server to resume normal database operations.

The value of ONDBSPACEDOWN has no affect on temporary dbspaces. For temporary dbspaces, the database server continues processing regardless of the ONDBSPACEDOWN setting. If a temporary dbspace requires fixing, you can drop and recreate it.

When ONDBSPACEDOWN is set to 2, the database server continues processing to the next checkpoint and then suspends processing of all update requests. The database server repeatedly retries the I/O request that produced the error until the dbspace is repaired and the request completes or the database server administrator intervenes. The administrator can use onmode -O to mark the dbspace down and continue processing while the dbspace remains unavailable or use onmode -k to halt the database server.
Important: This 2 setting for ONDBSPACEDOWN can affect the performance for update requests severely because they are suspended due to a down dbspace. When you use this setting for ONDBSPACEDOWN, be sure to monitor the status of the dbspaces.
When you set ONDBSPACEDOWN to 1, the database server treats all dbspaces as though they were critical. Any nonmirrored dbspace that becomes disabled halts normal processing and requires a cold restore. The performance impact of halting and performing a cold restore when any dbspace goes down can be severe.
Important: If you decide to set ONDBSPACEDOWN to 1, consider mirroring all your dbspaces.

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