Entering content frame

 Special Threads 

Special threads are operating system threads. Among other things, they are responsible for accessing external resources. A database instance has the following special threads:

Coordinator

The coordinator monitors all threads of the database instance. It is the first thread to be created when the database instance is started. It coordinates the start processes of the other threads. If operating errors occur, the coordinator can stop other threads.

Requester

The requester accepts user logons to the database instance and assigns them to a user task in a user kernel thread.

Console thread

The console thread processes requests from the XCONS tool (database console).

Clock thread

The clock thread determines internal times, for example, the time it takes to execute an SQL statement. It is only used on Microsoft Windows.

Dev threads

Dev threads are responsible for processing write and read requests to and from the volumes.

The number of dev threads is primarily dependent on the number of volumes in the database instance. Under normal circumstances, two dev threads are activated for every data volume and every log volume. Only one dev thread is activated for writing the database trace, if it is enabled.

The dev threads are numbered sequentially (dev<n>). The dev thread dev0 has the special responsibility of coordinating and monitoring the other dev threads.

Temporary dev threads

To make data backups, temporary dev threads (asdev<i>) are activated for reading and writing data.

Timer

Timers monitor timeouts and are also responsible for other internal time-dependent controls.

 

 

Leaving content frame