IBM Tivoli Monitoring > Version 6.3 Fix Pack 2 > Installation Guides > Installation Guide > Performance tuning > Tivoli Data Warehouse > Relational database design and performance tuning for DB2 Database servers > Database design details
IBM Tivoli Monitoring, Version 6.3 Fix Pack 2
Table spaces
A table space is a physical storage object that provides a level of indirection between a database and the tables stored within the database. It is made up of a collection of containers into which database objects are stored.
A container is an allocation of space to a table space. Depending on the table space type, the container can be a directory, device, or file. The data, index, long field, and LOB portions of a table can be stored in the same table space, or can be individually broken out into separate table spaces.
When you are working with database systems, the main objective is your ability to store and retrieve data as quickly and efficiently as possible. One important consideration when designing your database or analyzing a performance problem on an existing database is the physical layout of the database itself.
DB2 provides support for two types of table spaces:
- System Managed Space (SMS)
- Stores data in operating system files. This type is an excellent choice for general-purpose use, providing good performance with little administration cost.
- Database Managed Space (DMS)
- Includes database manager control of the storage space. A list of devices or files is selected to belong to a table space when it is defined. The DB2 database manager manages the space on those devices or files. Some additional administration cost is incurred with DMS table spaces because the size of the pre-allocated files is monitored and adjusted. Altering an existing container or adding a new container to it can increase the DMS table space size.
- Performance and table space types
DMS table spaces usually perform better than SMS table spaces because they are pre-allocated and do not use up time extending files when new rows are added. DMS table spaces can be either raw devices or file system files. DMS table spaces in raw device containers provide the best performance because double buffering does not occur. Double buffering, which occurs when data is buffered first at the database manager level and subsequently at the file system level, might be an additional cost for file containers or SMS table spaces.
- File system caching on a Windows system
For Windows systems caching, the operating system might cache pages in the file system cache for DMS file containers and all SMS containers. For DMS device container table spaces, the operating system does not cache pages in the file system cache.
Parent topic:
Database design details