Understanding the SMI Tables

The SMI (system-monitoring interface) consists of tables and pseudo-tables that the database server maintains automatically. While the SMI tables appear to the user as tables, they are not recorded on disk as normal tables are. Instead, the database server constructs the tables in memory, on demand, based on information in shared memory at that instant. When you query an SMI table, the database server reads information from these shared-memory structures. Because the database server continually updates the data in shared memory, the information that SMI provides lets you examine the current state of your database server.

The SMI tables provide information about the following topics:
  • Auditing
  • Checkpoints
  • Chunk I/O
  • Chunks
  • Database-logging status
  • Dbspaces
  • Disk usage
  • Environment variables
  • Extents
  • Locks
  • Networks
  • SQL statement cache statistics
  • SQL statements
  • System profiling
  • Tables
  • User profiling
  • Virtual-processor CPU usage

The data in the SMI tables changes dynamically as users access and modify databases that the database server manages.