Asynchronous log service

Asynchronous log service, or ALS, enables great scalability in Adaptive Server, providing higher throughput in logging subsystems for high-end symmetric multiprocessor systems.

You cannot use ALS if you have fewer than 4 engines. If you try to enable ALS with fewer than 4 online engines an error message appears.

Enabling ALS

You can enable, disable, or configure ALS using the sp_dboption stored procedure.

sp_dboption <db Name>, "async log service", 													"true|false"

Issuing a checkpoint

After issuing sp_dboption, you must issue a checkpoint in the database for which you are setting the ALS option:

sp_dboption "mydb", "async log service", "true"
use mydb

checkpoint

Disabling ALS

Before you disable ALS, make sure there are no active users in the database. If there are, you receive an error message when you issue the checkpoint:

sp_dboption "mydb", "async log service", "false"
use mydb

checkpoint
-------------
Error 3647: Cannot put database in single-user mode. Wait until all users have logged out of the database and issue a CHECKPOINT to disable "async log service".

If there are no active users in the database, this example disables ALS:

sp_dboption "mydb", "async log service", "false"
use mydb

checkpoint
-------------

Displaying ALS

You can see whether ALS is enabled in a specified database by checking sp_helpdb.

sp_helpdb "mydb"
----------
mydb					3.0 MB sa							2
		July 09, 2002
		select into/bulkcopy/pllsort, trunc log on chkpt,

			async log service