The ALS is an optional process that flushes log data to the
    after-image journal (.aij) file. All database servers deposit
    transaction log data in a cache located in the database global
    section. If the ALS is active, it continuously flushes the log
    data to disk. Otherwise, server processes might block temporarily
    if the cache in the global section is full. The ALS should be
    started only when AIJ processing is a bottleneck. Typically,
    multiuser databases with medium to high update activity can
    benefit from using the ALS.

    You can start the ALS either manually, using the RMU Server
    After_Journal Start command, or automatically when the database
    is opened (by specifying LOG SERVER IS AUTOMATIC in the SQL ALTER
    DATABASE command). By default, the ALS startup is set to manual.