Instances

An instance is a logical database manager environment where you catalog databases and set configuration parameters. Depending on your needs, you can create more than one instance on the same physical server providing a unique database server environment for each instance.

Note: For non-root installations on Linux® and UNIX operating systems, a single instance is created during the installation of your Db2® product. Additional instances cannot be created.
Attention: Instances cannot be shared across different Db2 versions.

You can use multiple instances to do the following:

  • Use one instance for a development environment and another instance for a production environment.
  • Tune an instance for a particular environment.
  • Restrict access to sensitive information.
  • Control the assignment of SYSADM, SYSCTRL, and SYSMAINT authority for each instance.
  • Optimize the database manager configuration for each instance.
  • Limit the impact of an instance failure. In the event of an instance failure, only one instance is affected. Other instances can continue to function normally.

Multiple instances will require:

  • Additional system resources (virtual memory and disk space) for each instance.
  • More administration because of the additional instances to manage.

The instance directory stores all information that pertains to a database instance. You cannot change the location of the instance directory once it is created. The directory contains:

  • The database manager configuration file
  • The system database directory
  • The node directory
  • The node configuration file (db2nodes.cfg)
  • Any other files that contain debugging information, such as the exception or register dump or the call stack for the Db2 database processes.

Terminology:

Bit-width
The number of bits used to address virtual memory: 32-bit and 64-bit are the most common. This term might be used to refer to the bit-width of an instance, application code, external routine code. 32-bit application means the same things as 32-bit width application.
32-bit Db2 instance
A Db2 instance that contains all 32-bit binaries including 32-bit shared libraries and executables.
64-bit Db2 instance
A Db2 instance that contains 64-bit shared libraries and executables, and also all 32-bit client application libraries (included for both client and server), and 32-bit external routine support (included only on a server instance).