How to handle the output device

The output devices are controlled by the dp0 menu (the more colorful one of the two windows that come up by default if you start the run). The window is shown in figure 2.


This window has three areas:
1. top window: a listing of defined streams and their status (open, closing, closed).
2. middle window: output status from the tape handeling processes (if you think something went wrong, then check this window for messages).
3. bottom third has control buttons (see below).

By default you write to trashcan. If you want to write data to disk or tape you have to do this before you start the run. In order to start writing to tape you have to do two things:
1. select an output device
2. open it.

• how to select the output device
  For this you use the left area (configure streams). In most of the cases you either want to 1. write to disk file, 2. write to one tape device, 3. write the standard pass 0 configuration. For each of these three situations there are standard buttons.
  (Of course you can define and delete data streams as you want - this will be described in more detail in a latter section).

• how to open/close the output device
  After you selected the output device you open it by pressing one of the buttons on the right area labled ``open/close streams''. If there is only one stream, then this is the default stream. If there are more streams and you want to open/close them all at the same time, press open/close all stream button. If you have several streams defined but you only want to open one of them, select it (by clicking on it in the top text field) window and press open/close selected stream.
  At this point the tape label will appear between the status and the trigger information at the dp0_ui top window. This label is the default value and it will be incremented automatically. The format and philosophy of the labeling scheme will be described in the more detailed dp0_ui section. In addition a window will pop up. It is shown in figure 3 if the events are only written to one tape drive. Figure 4 shows the window if there is multistreaming to several tapes.
  In most cases the default label is the correct one and one simply has to press ``OK''. (For exceptions see the section on the dp0_ui interface.)
  If the output device is a disk file or ``trashcan'', then the tape label window will of course not show up.

• how to disable output temporarily
  Press the green bar at the bottom ``data taking enabled'' and toggle it to ``data taking disabled'' (color red). This option will only disable the tape writing of the defined output devices. The rest of the online system will run as before (see the section on the dp0's for more details).

 
Figure 3:   Tape label window for writing to one tape device.

 
Figure 4:   Tape label window for multistreaming to several tapes.