COMPATIBILITY FORCE_WRITETHRU enables the WRITETHRU filemode for all non-transaction files (which includes PREIMG files). The performance impact of WRITETHRU depends on whether COMPATIBILITY PREV610A_FLUSH is also enabled. See the descriptions in COMPATIBILITY FORCE_WRITETHRU and COMPATIBILITY PREV610A_FLUSH.
These options provide a good balance between update performance and recoverability of data in the event of an abnormal FairCom Server termination. They affect non-transaction files as follows:
Be sure to understand the impact of these file modes with respect to your file transaction mode in use, and type and vulnerability of your application data.