Global snapshots on partitioned database systems

On a partitioned database system, you can use the snapshot monitor to take a snapshot of the current partition, a specified partition, or all partitions. When taking a global snapshot across all the partitions of a partitioned database, data is aggregated before the results are returned.

Data is aggregated for the different element types as follows:

• Counters, Time, and Gauges

  Contains the sum of all like values collected from each partition in the instance. For example, GET SNAPSHOT FOR DATABASE XYZ ON TEST GLOBAL would return the number of rows read (rows_read) from the database for all partitions in the partitioned database instance.

• Watermarks

  Returns the highest (for high water) or lowest (for low water) value found for any partition in the partitioned database system. If the value returned is of concern, then snapshots for individual partitions can be taken to determine if a particular partition is over utilized, or if the problem is instance-wide.

• Timestamp

  Set to the timestamp value for the partition where the snapshot monitor instance agent is attached. Note that all timestamp values are under control of the timestamp monitor switch.

• Information

  Returns the most significant information for a partition that may be impeding work. For example, for the element appl_status, if the status on one partition was UOW Executing, and on another partition Lock Wait, Lock Wait would be returned, since it is the state that's holding up execution of the application.

You can also reset counters, set monitor switches, and retrieve monitor switch settings for individual partitions or all partitions in your partitioned database.