ASE doesn't have the ability to 'increase' the dataserver pagesize.
You'll have to create a new dataserver of the desired page size.
And unfortunately you cannot dump-n-load databases between dataservers with different page sizes.
To get stuff (eg, logins, roles, tables, procs, data, etc) out of the old dataserver into the new dataserver you'll have to go through a lengthy manual process (eg, sybmigrate utility that comes with ASE, DDL extraction + bcp of data, etc).
