The dsync parameter ensures Adaptive Server can recover data from devices on file systems.
By default, Adaptive Server disables dsync for file system devices. You can set or reset dsync using the disk init and disk reinit commands. When dsync is set to false (off), cached I/O is used.
Immediately after upgrading, check that either dsync or directio is set for the file system devices. See also sp_helpdevice in the Reference Manual: Procedures