In Adaptive Server version 15.7 and later, alter database includes the log off parameter, which removes unwanted portions of a database log, allowing you to shrink log space and free storage without re-creating the database.
log off may be particularly helpful after running the fully logged option for database operations, such as select into, alter table, or reorg rebuild, when the database ends up with extra allocated space that is no longer needed.
See "Fully Recoverable DDL" in this document and "Creating and Managing User Databases" in the System Administration Guide, Volume 2.