Reserves one or multiple devices to prevent other sessions from access the devices. You must reserve a device before using it.

To reserve a device that has been reserved by another session with Read/Write access, you can close the session, unreserve the device, or use the same reservation group name as that of the device. You can directly reserve a device that has been reserved by another session with Read Only access.


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Inputs/Outputs

  • cgenclassrntag.png session in —

    session in specifies the session to access for the given action.

  • cgenclassrntag.png devices —

    devices specifies the name(s) of the device(s) to access. For multiple devices, use a comma-delimited list.

  • ci32.png reservation access (Read/Write) —

    reservation access (Read/Write) specifies how you plan to access the session. The default is Read/Write.

  • cstr.png reservation group —

    reservation group allows sharing read/write reservations. When multiple sessions attempt to simultaneously reserve the same devices for read/write access, the reservation succeeds if they have the same reservation group. Reservation fails if they do not have the same reservation group. If you specify an empty string or do not specify this parameter, only one session can reserve the devices for read/write access at a time. Read-only reservations may share devices without specifying a reservation group.

  • cerrcodeclst.png error in (no error) —

    error in (no error) describes error conditions that occur before this node runs. This input provides standard error in functionality.

  • cdbl.png reservation timeout (5 sec) —

    reservation timeout (5 sec) specifies the maximum amount of time, in seconds, to wait to reserve a device that has been reserved by other sessions. The default is 5. If you set reservation timeout to -1, reservation timeout uses the value of the Session.ReservationTimeout property.

    If reservation_timeout is greater than 0 and reservation access is Read/Write, a deadlock may occur when multiple sessions that use the same group name try to reserve multiple devices. The following table shows a deadlock condition that occurs when two sessions try to reserve two modules.

    session 1 session 2
    Reserve module 1 Reserve module 2
    Try to reserve module 2 Try to reserve module 1
    Wait for module 2 Wait for module 1

    Both session 1 and session 2 return errors when timeout expires. To avoid the deadlock, ensure that session 1 and session 2 reserve modules in the same order. If session 1 reserves module 1 first and then reserves module 2, ensure that session 2 also reserves module 1 first and then reserves module 2.

  • igenclassrntag.png session out —

    session out is a copy of the session in reference.

  • ierrcodeclst.png error out —

    error out contains error information. This output provides standard error out functionality.