Shrink a SQL Anywhere 12 database
You can't shrink SQL Anywhere databases online.

The "correct" way to do it is to unload/reload it in a new database.

It's easy to do it via Sybase Central. Via command line it is the dbunload command with the -an command line switch. See Unload utility (dbunload) in the documentation.

A shrunk database is not by default faster than an "unshrinked" database.