Monitoring Checkpoint Information

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Monitoring Checkpoint Information

Monitor checkpoint activity to determine basic checkpoint information. This information includes the number of times that threads had to wait for the checkpoint to complete. This information is useful for determining if the checkpoint interval is appropriate. For information on tuning the checkpoint interval, see your IBM Informix Dynamic Server Performance Guide.

To monitor checkpoints, use the following commands.

Utility	Command	Additional Information
Command line or ISA	onstat -m	View the last 20 lines in the message log. If a checkpoint message does not appear in the last 20 lines, read the message log directly with a text editor. The database server writes individual checkpoint messages to the log when the checkpoint ends. If a checkpoint occurs, but the database server has no pages to write to disk, the database server does not write any messages to the message log.
Command line or ISA	onstat -p	Obtains these checkpoint statistics: numckpts: Number of checkpoints that occurred since the database server was brought online. ckptwaits: Number of times that a user thread waits for a checkpoint to finish. The database server prevents a user thread from entering a critical section during a checkpoint.
ON–Monitor (UNIX)	Status > Profile	The Checkpoints and Check Waits fields display the same information as the numckpts and ckpwaits fields in onstat -p.

Utility

Command

Additional Information

Command line or ISA

onstat -m

View the last 20 lines in the message log.

If a checkpoint message does not appear in the last 20 lines, read the message log directly with a text editor. The database server writes individual checkpoint messages to the log when the checkpoint ends.

If a checkpoint occurs, but the database server has no pages to write to disk, the database server does not write any messages to the message log.

Command line or ISA

onstat -p

Obtains these checkpoint statistics:

numckpts: Number of checkpoints that occurred since the database server was brought online.
ckptwaits: Number of times that a user thread waits for a checkpoint to finish. The database server prevents a user thread from entering a critical section during a checkpoint.

ON–Monitor (UNIX)

Status > Profile

The Checkpoints and Check Waits fields display the same information as the numckpts and ckpwaits fields in onstat -p.