Overview of Tasks

Use

The database system executes actions requested by users or the kernel in tasks.

Overview of Important Tasks

Name

Description

Event Task

The event task accepts events that are created in the kernel and communicates them externally.

Log Writer

The log writers write log entries from the log queue to the log area, for example due to a COMMIT or a savepoint.

Pager (data writer)

Pagers write the data from the data cache to the data volumes with each savepoint. Writing a savepoint can take a long time for a large data cache. If necessary, the pagers also become active between the end of a savepoint and the start of the next one, to save the changed data asynchronously.

At restart, the pagers read the converter pages from the data volumes to the converter. The system calculates the number of pagers required. It is primarily dependent on the size of the data cache and the number of data volumes.

Server Task

The server tasks parallelize database functions. They are required, for example, to back up data and log entries, create indexes and to permanently delete tables. During a restart, they import log entries and process transactions in parallel.

You can configure the number of server tasks that are available using the MAXSERVERTASKS special database parameter.

Server tasks can have special names that reflect how they are used, for example Savepoint, BackupMedium, BackupVolume, AutosaveCoordinator, AutosaveMedium.

Timer Task

The timer task is responsible for timeouts of SQL lock requests and checks whether log entries can be backed up.

Trace Writer Task

The trace writer task writes the trace entries in the working memory when the database trace is switched on.

User Task

User tasks execute SQL statements.

When a database user opens a database session, the database system assigns one user task to this database user.

You can configure the number of available user tasks using the MAXUSERTASKS special database parameter.

Utility Task

The utility task performs administration tasks.

Activities

To display information about tasks, use the Database Manager or XCONS or in SAP systems the database assistant or liveCache assistant. See

?     Database Manager GUI, Displaying Database Sessions

?     Database Manager CLI, show

?     XCONS documentation

?     Database Administration in CCMS: MaxDB, Task Manager

See also:

Overview of the Task States

Process Structure