I have managed to use multifilesink. Here is the pipeline I wrote using GStreamer. Recreating it in DeepStream is just using those elements and setting properties.
gst-launch-1.0 -e nvarguscamerasrc sensor_id=0 sensor_mode=0 ! capsfilter caps="video/x-raw(memory:NVMM), width=3840, height=2160, framerate=60/1, format=NV12" ! queue ! nvv4l2h265enc iframeinterval=60 idrinterval=1 insert-sps-pps=true ! h265parse ! multifilesink location="frame%03d.h265" next-file="max-duration" max-file-duration=1000000000
It saves raw hevc/h265 files every 1 second.