Checkpointing (Informix) (SAP Library - Monitoring in the CCMS)

Checkpointing (Informix)

Definition

A checkpoint is the action or point of time when Informix has written all modified pages from the buffers to disk, so the database is physically consistent. The following logs are maintained by the Informix database and are relevant to checkpoints:

Physical log

This enables restore to a consistent database state as of the last checkpoint in the event of a crash or power failure.

Logical log

This is used for:

Transaction logging, to enable rollbacks of aborted transactions
Logging of all changes to the database, to enable a restore as of the last archive and up to the point of failure

Use

You can use the database overview of the SAP/Informix database monitor to view checkpointing.

The size of the physical log is relevant for checkpointing because a checkpoint is forced when the physical log becomes 75% full. The figures Chkpoint Correlation % and Physical Correlation % are intended to give an approximate idea of how often checkpoints have occurred because the checkpoint interval has finished and how often because the physical log is 75% full. The checkpoint interval has a default value of 900 seconds in an SAP installation.

The figures are approximate and so do not always add up to exactly 100%.

See also:

CKPTINTVL (Informix)