Download Performance Guide for Informix Extended Parallel Server

Configuration Parameters That Affect Checkpoints
ONDBSPDOWN
The ONDBSPDOWN configuration parameter specifies the database server
behavior when an I/O error indicates that a dbspace is down. By default, the
database server marks any dbspace that contains no critical database server
data as down and continues processing. Critical data includes the root
dbspace, the logical log, and the physical log. You must back up all logical
logs and then perform a warm restore on the down dbspace to restore access
to it.
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
ONDBSPDOWN. In such an event, you must perform a cold restore of the
database server to resume normal database operations.
When ONDBSPDOWN 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 is complete or until 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: If you set ONDBSPDOWN to 2, be sure to monitor the status of your
dbspaces continuously.
When ONDBSPDOWN is set 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 the database server and performing a cold restore when any
dbspace goes down can be severe.
Important: If you decide to set ONDBSPDOWN to 1, consider mirroring all your
dbspaces.
USEOSTIME
The USEOSTIME parameter specifies whether the database server uses
subsecond precision when it gets the time for SQL statements. If database
applications do not require subsecond precision, set USEOSTIME to 0 to avoid
unnecessary calls to the operating-system clock.
Effect of Configuration on I/O
5-25