Adaptive Server Enterprise version 12.5.1 provides automatic expansion of databases and devices. Databases can be configured to expand automatically when they run out of space.
The automatic database expansion stored procedure sp_dbextend allows you to install thresholds that identify which devices have room and then appropriately alter the database—and the segment where the threshold was fired—on these devices.
sp_dbextend is the user interface for the automatic expansion process. DBAs use it to:
Define site-specific rules for individual segments and devices
Change user-specified policies and system-supplied default behaviours
Examine the current state of the rules
DBAs can also use this interface to execute trial simulations of the database expansion machinery, and if necessary, to manually perform a database expansion without waiting for the automatic expansion process to be scheduled.
After you set up the database for automatic expansion, when a database grows to its free space threshold, internal mechanisms fire, increasing the size of the database by the amount of space specified by expansion policies. The automatic expansion process measures the amount of room left on all devices bound to the database. If there is sufficient room on the device, the database continues to grow. If any devices are configured for expansion, those devices are expanded next, followed by expansion of the database on those devices. The automatic expansion process runs as a background task and generates informational messages in the server’s error log about its progress.
The automatic expansion process requires new installation procedures. You install it using the installdbextend script, which loads new rows into master.dbo.sysattributes—rows that describe defaults for autoexpansion in a database or in a device. You can install the automatic expansion process in one or more databases or one or more devices.
You can configure automatic expansion to run with server-wide default expansion policies, or you can customize it for individual segments in specified databases.You can install thresholds on key segments on which tables with critical data reside, allowing you to have a fine degree of control over how Adaptive Server meets the data space requirements for different kinds of tables. If your site has key tables with large volumes of inserts, you can bind these tables to specific segments, with site-specific rules of extending that segment. This enables you to avoid outages that can occur in a production environment due to large loads to such key tables.
Automatic expansion procedures allow you to simulate the expansion processes based on your chosen policies. This simulation allows you to make sure the expansion processes work without jeopardizing your production environment.
The automatic expansion procedure does not create new
devices; it only alters the size of the database and segment on
existing devices to which the segment currently maps.
For more information, see Chapter 30, “Automatic Database Expansion,” in the System Administration Guide.
