The system monitor accumulates information for a database only while it is active. If all applications disconnect from a database and the database deactivates, then the system monitor data for that database is no longer available. You can keep the database active until your final snapshot has been taken, either by starting the database with the ACTIVATE DATABASE command, or by maintaining a permanent connection to the database.
Snapshot monitoring requires an instance attachment. If there is not an attachment to an instance, then a default instance attachment is created. An instance attachment is usually done implicitly to the instance specified by the DB2INSTANCE environment variable when the first database system monitor API is invoked by the application. It can also be done explicitly, using the ATTACH TO command. Once an application is attached, all system monitor requests that it invokes are directed to that instance. This allows a client to monitor a remote server by simply attaching to the instance on it.
In partitioned database environments, snapshots can be taken at any partition of the instance, or globally using a single instance connection. A global snapshot aggregates the data collected at each partition and returns a single set of values.
In Db2® pureScale® environments, snapshots can be taken at any member or globally. A global snapshot aggregates the data collected at each member and returns a single set of values.
You can capture a snapshot from the CLP, from SQL table functions, or by using the snapshot monitor APIs in a C or C++ application. A number of different snapshot request types are available, each returning a specific type of monitoring data. For example, you can capture a snapshot that returns only buffer pool information, or a snapshot that returns database manager information. Before capturing a snapshot, consider if you need information from monitor elements that are under monitor switch control. If a particular monitor switch is off, the monitor elements under its control will not be collected.