Using RSX-11M BRU under VAX/VMS Frank J. Nagy Fermi National Accelerator Laboratory P. O. Box 500 Mail Stop 306 Batavia, IL 60510 1.0 Introduction This article is a description of how one may make use of the RSX-11M Backup and Restore Utility (BRU) under VAX/VMS. It is the result of a bit of experimentation with using BRU and no effort into investigating the internals of BRU. The executable images of BRU are built using the BRU object library and build files from an RSX-11M distribution kit. These files may be found on volume RLUTIL in an RL01/RL02 distribution kit. The task builder command file (BRUBLD.CMD) and the overlay description file (BRUBLD.ODL) were editted to remove the references to the logical devices and explicit UFD usage. For RSX-11M V4.0, these files had to be created by executing the BRUBLD.BLD from a specially created outer command file (to make appropriate definitions for the symbols used in BRUBLD.BLD). For the purposes of experimentation, two versions of BRU were built and stored as executable images (.EXE files) in SYS$SYSTEM:. These were BRU3 from the RSX-11M V3.2 distribution and BRU4 from the RSX-11M V4.0 distribution. The BRU images could be invoked from DCL using the MCR command or by using RUN. Most of the efforts to date have centered around the V4.0 BRU. 2.0 Reading BRU Tapes The primary objective was to be able to read BRU tapes on the VAX (such tapes having been written by RSX systems). The goal is to be able to read the RSX SIG tapes on the VAX as all the software development work for the control system RSX-11M systems is done on VAX's. It was found to be possible to read a V4.0 BRU tape on the VAX providing the following restrictions were followed: 1. The input tape must be mounted as a foreign volume (/FOREIGN). 2. The output disk must also be mounted as a foreign volume (/FOREIGN). In this case the logical I/O (LOG_IO) privilege appears to be unnecessary. Page 2 3. BRU must be told to initialize the output disk volume itself (possibly with a /INITIALIZE in the BRU command line). This must be done even if reading a single UFD from the tape. In reading from a BRU tape to disk one is restricted to writing to a scratch disk as any other information on the disk is wiped when BRU initializes the volume. BRU will quite happily restore the entire tape or just a single UFD to this scratch disk. Just for clarity here is what one cannot do with BRU on the VAX. For the most part trying to do one of these in reading a BRU tape will result in a "No privilege" error message from BRU: 1. BRU cannot output to any ODS-2 disk. This includes not being able to write to your current directory using device SY:. 2. BRU will also not allow one to write on an ODS-1 disk that is already initialized (that is you use the /NOINITIALIZE qualifier on the BRU command). This does not work whether the output disk volume is mounted as a Files-11 volume or as a foreign volume (/FOREIGN) and irrespective of the LOG_IO privilege. V3.2 BRU The above statements apply to RSX-11M V4.0 BRU only. We have not yet succeeded in using V3.2 BRU to read (a V3.2 BRU) tape to disk as of this time. 3.0 Writting BRU Tapes Although the objective was to be able to read BRU tapes on the VAX (since our PDP-11's have no tape drives), it was decided to try writting a tape with BRU just for grins. This worked quite well, but once again is subject to some restrictions: 1. The output tape must be mounted as a foreign volume (/FOREIGN). 2. The input disk can be mounted as foreign in which case the LOG_IO privilege was unnecessary. 3. The input disk can also be mounted as a Files-11 volume. In this case the LOG_IO privilege is required and the BRU command line must include a /MOUNTED qualifier. 4. The input disk must be an ODS-1 volume. BRU seems to work equally well whether the entire disk is written to tape or just a single UFD is written. However, BRU Page 3 is again unable to handle even the current directory of an ODS-2 disk. When V3.2 BRU was used to write a tape, a surprise resulted as writing with V3.2 BRU seems to work just as well as it does for V4.0 BRU. However, the resulting tape was unable to be read back onto a disk so one cannot really be sure about V3.2 BRU. Note that using BRU to list the contents of the tape (with /DIRECTORY) seems to work on the VAX with either the V3.2 or V4.0 BRU. This article has been submitted to the RSX SIG's The ___ Multi-Tasker and the VAX Systems SIG's Pageswapper in an effort ____________ ___________ to reach both communities of users.