The db2top command provides a unified, single-system view of a multi-partition database or single-partition database on the AIX®, Linux® and Solaris operating systems. It can be used to quickly identify global problems, or specific database partition problems in the system. By combining snapshot information from each database partition, the utility can provide a dynamic real-time view of a running DB2® system.db2top provides quick overview of tablespace, bufferpool, session, and other activities. It allows to capture snapshots over time and then automatically analyze them for performance. All this is provided through a simple-to-use text interface.
If you want to know more about db2top, I recommend to start with this developerWorks article and of course to visit the DB2 Information Center for the command details.