Asynchronous log service, or ALS, enables scalability in Adaptive Server, providing higher throughput in logging subsystems for high-end symmetric multiprocessor systems.
For every database on which ALS is enabled, one engine predominantly performs log I/O, so ALS is beneficial only when the contention on the log semaphore is higher than the processing power of one engine.
You cannot use ALS if you have fewer than four engines.
Use sp_dboption to enable, disable, or configure ALS
sp_dboption database_name, "async log service", "true|false"
checkpoint (which writes all dirty pages to the database device) is automatically executed as part of sp_dboption.
This example enables ALS for mydb:
sp_dboption "mydb", "async log service", "true"
Before you disable ALS, make sure there are no active users in the database. If there are, you receive an error message.
This example disables ALS:
sp_dboption "mydb", "async log service", "false"
Use sp_helpdb to see whether ALS is enabled in a specified database:
sp_helpdb "mydb" name db_size owner dbid created durability status ---- ------------- ----- ---- ------------ ---------- --------------- mydb 3.0 MB sa 5 July 09, 2010 full select into/bulkcopy/pllsort, trunc log on chkpt, async log service device_fragments size usage created free kbytes ------------------------------ ------------ -------------------- ------------------------- ---------------- master 2.0 MB data only Jul 2 2010 1:59PM 320 log_disk 1.0 MB log only Jul 2 2010 1:59PM not applicable -------------------------------------------------------------- log only free kbytes = 1018 device segment -------- ---------- log_disk logsegment master default master system