/Experiment ODB tree

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Creating the /Experiment tree

The /Experiment ODB tree is created automatically when the ODB is first created.

Purpose

The /Experiment ODB tree contains information relevent to the experiment. Other optional keys are added by mhttpd or by the user to customize their experiment.

Examples

When initially created, the /Experiment tree contains the following keys:

[local:midas:S]/>ls -lrt /experiment
Key name                        Type    #Val  Size  Last Opn Mode Value
---------------------------------------------------------------------------
Experiment                      DIR
   Name                        STRING  1     32    14s  0   RWD  midas
   Buffer sizes                DIR
       SYSMSG                  DWORD   1     4     11h  0   RWD  100000

The following example shows the /Experiment tree for a typical experiment :

[local:deap:R]/>ls -lrt /experiment
Key name                        Type    #Val  Size  Last Opn Mode Value
---------------------------------------------------------------------------
Experiment                      DIR
   Name                        STRING  1     32    7s   0   RWD  midas
   Buffer sizes                DIR
       SYSMSG                  DWORD   1     4     23h  0   RWD  100000
       SYSTEM                  DWORD   1     4     23h  0   RWD  640000000
       BUF0                    DWORD   1     4     23h  0   RWD  80000000
       BUF1                    DWORD   1     4     23h  0   RWD  80000000
       .......    other user-defined buffers not shown  
   MAX_EVENT_SIZE              DWORD   1     4     23h  0   RWD  4194304
   Menu Buttons                STRING  1     256   5h   0   RWD  Status, ODB, Messages, Elog, Alarms, Programs, History, MSCB, Sequencer, Config, Help
   Transition debug flag       INT     1     4     23h  0   RWD  0
   Transition connect timeout  INT     1     4     23h  0   RWD  10000
   Transition timeout          INT     1     4     23h  0   RWD  120000
   edit on start               DIR
       experiment number               DWORD   1     4     2h   0   RWD  9499
       experimenter                    STRING  1     32    2h   0   RWD  gdm
       sample                          STRING  1     36    2h   0   RWD  NA
       temperature                     STRING  1     32    2h   0   RWD  300.000(0.000)K
       field                           STRING  1     32    2h   0   RWD  19000.2(0.0)G
       comment-> /Experiment/run parameters/comment
                                       STRING  1     80    2h   0   RWD  Testing with low beam
       Write Data -> /Logger/Write data
                                       BOOL    1     4     2h   0   RWD  n
       Number of cycles -> /Equipment/FIFO_acq/frontend/hardware/num cycles
                                       DWORD   1     4     2h   0   RWD  0
   Parameter Comments          DIR                   
       field                           STRING  1     32    >99d 0   RWD  Entered in Tesla unit
       Num cycles                      STRING  1     80    >99d 0   RWD  Stop run after num cycles is reached. Enter 0 to disable (free running)
   Run Parameters              DIR
       Comment                         STRING  1     80    2h   0   RWD  Testing with low beam
       Run Description                 STRING  1     256   7h   0   RWD  Sequencer Tests
       Number of channels              DWORD   1     4     2h   0   RWD  20
   Lock when running           DIR
       Num channels -> /Run Parameters/number of channels
                                       DWORD   1     4     2h   0   RWD  20
   edit on sequence            DIR
       title                           STRING  1     128   2h   0   RWD  none
       experiment number               DWORD   1     4     2h   0   RWD  9438
       experimenter                    STRING  1     32    2h   0   RWD  gls
       sample                          STRING  1     36    2h   0   RWD  NA
       run description -> /Experiment/run parameters/run description
                                       STRING  1     256   7h   0   RWD  Sequencer Tests
       Write Data -> /Logger/Write data
                                       BOOL    1     4     2h   0   RWD  n
       Number of cycles -> /Equipment/FIFO_acq/frontend/hardware/num cycles
                                       DWORD   1     4     2h   0   RWD  0
   Prevent start on alarms     BOOL    1     4     22h  0   RWD  n
   Prevent start on required   BOOL    1     4     22h  0   RWD  n
   Status items                DIR
       Experiment Name -> /Experiment/Name
                               STRING  1     32    7s   0   RWD  midas
   Start-Stop Buttons          BOOL    1     4     5h   0   RWD  y
   Pause-Resume Buttons        BOOL    1     4     5h   0   RWD  n

Keys in /Experiment tree

The keys in the ODB /Experiment tree are described in the following sections.

Name

• Type: STRING
• Default:

This key in the /Experiment tree contains the name of the experiment. Filled automatically when the ODB is created.

---

Buffer Sizes subtree

• Type: DIR

This key in the /Experiment tree is a subtree to contain the sizes of the Midas Buffers for the experiment. Created with default values. The sizes can be changed to optimize the memory usage. See Event Buffer Size(s) for details. Other user-defined buffers may be present (e.g. for event filtering).

---

SYSMSG

• Type: DWORD
• Default: 100000 Bytes

This key in the /Experiment/Buffer Sizes subtree contains the size of SYSMSG buffer. This buffer is used for MIDAS messages.

---

SYSTEM

• Type: DWORD
• Default: 8MBytes

This key in the /Experiment/Buffer Sizes subtree contains the size of SYSTEM buffer. See Event Buffer for details.

---

MAX_EVENT_SIZE

• Type: DWORD
• Default: 4MBytes

This key in the /Experiment tree specifies the maximum event size that can be acquired. The default value is half the size of the SYSTEM buffer. It can be increased if required (see Event Buffer).

---

Menu Buttons

• Type: STRING
• Default: "Start, Pause, ODB, Messages, ELog, Alarms, Programs, History, Sequencer, Config, Help"

This key in the /Experiment tree is added automatically by mhttpd to allow the Menu buttons that appear on the Main Status Page to be customized by removing unnecessary buttons or by changing their order. Without the "Pause" being present in the list of menu buttons, the run cannot be paused/resumed, but only started/stopped. This is required by some experiments.

If MSCB support is built into MIDAS, the MSCB Menu button will also be shown.

---

Transition debug flag

• Type: INT
• Default: 0

This key in the /Experiment tree contains a flag that, if set to 1, causes messages reporting transition progress to be output.

---

Transition connect timeout

• Type: INT
• Default: 10000

This key in the /Experiment tree contains the value of timeout for remote rpc connect

---

Transition timeout

• Type: INT
• Default: 120000

This key in the /Experiment tree constains the value of timeout for transition

---

Prevent start on alarms

• Type: BOOL
• Default: "n"

This key in the /Experiment tree if set true will prevent the run from starting if an alarm is true, i.e. the run start procedure will fail if an alarm has been Triggered for a client, provided a valid alarms class has been entered in the client's Alarm class key.

---

Prevent start on required program

• Type: BOOL
• Default: "n"

This key in the /Experiment tree if set true ("y") will prevent the run from starting if one of the required clients is not running. A client is flagged as "required" by setting the ODB key Required to "y".

---

Start-Stop Buttons

• Type: BOOL
• Default: "y"

By default Start/Stop buttons are shown on the mhttpd main status page. These buttons can be suppressed by setting this key in the /Experiment tree FALSE.

---

Pause-Resume Buttons

• Type: BOOL
• Default: "n"

By default Pause/Resume buttons are shown on the mhttpd main status page. These buttons can be suppressed by setting this key in the /Experiment tree FALSE.

---

Edit on Start subtree

• Type: DIR

This optional subdirectory in the /Experiment tree may contain user-defined parameters which will be displayed for editing at the beginning of each run. See Edit-on-start Parameters for details.

---

Parameter Comments subtree

• Type: DIR

This optional subdirectory in the /Experiment tree may contain user-defined parameter comments that give more information about the Edit-on-start Parameters.

---

Status items subtree

• Type: DIR

This key in the /Experiment tree is a subtree which by default contains a link to the experiment name. Any links or keys created by the user in this optional subdirectory will be displayed on the mhttpd main status page.

---

Lock when running subtree

• Type: DIR

This optional subdirectory in the /Experiment tree contains user-defined links to ODB parameters to prevent them being changed when the run is in progress. See Lock when running for details.

---

Security subtree

• Type: DIR

This optional subtree in the /Experiment tree is created when the odbedit commands passwd or webpasswd are issued. It enables a user to set up security features. See Security

---

Password

• Type: STRING
• Default:

This key in the /Experiment/Security subtree contains the encrypted password. This Key is created when the odbedit command passwd is issued. See security for details.

Note

Do not set this key except through the odbedit command passwd. Setting an unencrypted password will lock you out of the ODB unless odbedit is listed as an allowed program.

---

Allowed hosts subtree

• Type: DIR

This subtree in the /Experiment/Security subtree is created when the odbedit command passwd is issued. When created, this subtree is empty. Optionally, it may contain user-defined names of remote hosts allowed to have free access (i.e. without password) to the current experiment. See allowed hosts.

---

Allowed programs subtree

• Type: DIR

This subtree in the /Experiment/Security subtree is created when the odbedit command passwd is issued. When created, this subtree is empty. Optionally, it may contain user-defined names of clients allowed to have free access (i.e. without password) to the current experiment. See allowed clients.

---

Web Password

• Type: STRING
• Default:

If web access restriction has been set up, this key in the /Experiment/Security subtree will contain an encrypted password for Web server access. This key is created by using the odbedit command webpasswd.

If this key is present, the user will be requested to provide the "Web Password" when accessing the requested experiment in "Write Access" mode. The "Read Only Access" mode is still available (without a password) to all users.

Edit on Sequence subtree

• Type: DIR

This optional subdirectory in the /Experiment tree may contain user-defined parameters which will be displayed for editing at the start of each Sequence). See Edit-on-Sequence Parameters for details.

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