public void setDiskSynchronous(boolean isSynchronous) {
    regionAttributes.diskSynchronous = isSynchronous;
    regionAttributes.setHasDiskSynchronous(true);
    if (regionAttributes.hasDiskWriteAttributes()) {
      DiskWriteAttributesFactory dwaf =
          new DiskWriteAttributesFactory(regionAttributes.diskWriteAttributes);
      dwaf.setSynchronous(isSynchronous);
      regionAttributes.diskWriteAttributes = dwaf.create();
    } else {
      if (isSynchronous) {
        regionAttributes.diskWriteAttributes =
            DiskWriteAttributesImpl.getDefaultSyncInstance();
      } else {
        regionAttributes.diskWriteAttributes =
            DiskWriteAttributesImpl.getDefaultAsyncInstance();
      }
    }
  }
Sets whether or not the writing to the disk is synchronous. Default is true.

@param isSynchronous boolean if true indicates synchronous writes
@since GemFire 6.5
geode-core/src/main/java/org/apache/geode/cache/AttributesFactory.java