The FairCom Server for Solaris uses O_DSYNC synchronous writes for the transaction logs when the COMPATIBILITY SYNC_LOG or COMPATIBILITY LOG_WRITETHRU configuration options are specified in the server configuration file.
Furthermore, it is expected the O_DSYNC writes are more efficient than O_SYNC writes. The FairCom Server uses O_DSYNC on systems that define this file open mode and uses O_SYNC on systems that do not define the O_DSYNC file open mode.
COMPATIBILITY DIRECT_IO, is available to revert to the previous behavior of direct I/O.
When the FairCom Server starts up, it writes either the message "Transaction logs using direct I/O." or "Transaction logs using synchronous I/O." to CTSTATUS.FCS to indicate which method of synchronous writes is in use. If neither COMPATIBILITY SYNC_LOG nor COMPATIBILITY LOG_WRITETHRU is specified in ctsrvr.cfg, neither of these messages is written to CTSTATUS.FCS as in that case the server performs asynchronous writes that are flushed by a separate call.