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

You can use the checkpoint to identify the one or more databasess or use an all clause.

checkpoint [all | [dbname[, dbname[, dbname.....]]]

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