The dsync option is used with the disk init and disk reinit commands. By default, Adaptive Server enables dsync for database device files. This option ensures that Adaptive Server can recover data from devices on file systems. However, dsync can cause a degradation in performance for device files that experience high write activity.
When you install a new 12.x Adaptive Server, by default dsync is set on for all devices.
When you upgrade a UNIX server that stores databases on UNIX file system devices, by default dsync is set:
on for the master device
off for all other devices.
See also, sp_deviceattr, and sp_helpdevice in the Reference Manual.