IBM s/390 manual Using tar to back up S/390 volumes

￿You can store S/390 backups on the ThinkPad disks, as Linux files. This provides logical backup of S/390 data, but does not provide protection against physical failure of disk drives.

￿You can ftp back up data (in a variety of formats) to another system. This provides protection against physical system failures.

There are two general formats for backed up data:

￿A file at the Linux level

These files contain a complete emulated S/390 volume. It is easy to restore the complete volume, but quite messy to restore a single S/390 data set.

￿A S/390 backup, using the OS/390 program ADRDSSU or equivalent

This backup would be written to a FakeTape file. Once written, this file can be treated as a normal Linux file. It could, for example, be ftped elsewhere for safety. This type of backup requires the use of OS/390 jobs and may be slower than purely Linux backup functions. It has the strong advantage that single S/390 data sets can be restored easily.

5.15.1Using tar to back up S/390 volumes

An emulated S/390 volume, such as a 3390 volume, is typically a single Linux file. You can back up this volume simply by copying the Linux file somewhere else in your Linux file system. It would be advisable to copy it to another physical disk drive, if possible, for obvious reasons. Emulated volumes are large Linux files and a ThinkPad has limited disk space. Using a compression program as part of the backup process is attractive.

We performed a small test, as follows:

$ tar -cvzf /holding/OS39RA.tarz /s390/OS39RA	note 1
tar: Removing leading ‘/’ from member names
$ ls -al /holding	note 2
$ cd /s390
$ mkdir untar	note 3
$ cd untar
$ tar -xzkwvf /holding/OS39RA.tarz	note 4
extract ‘s390/OS39RA’? y
$ ls -al
$ cmp -s /s390/OS39RA /s390/untar/OS39RA && echo ‘OK’	note 5
cmp /S390/OS39RA: File too large

1.We used a tar command to archive the file into a compressed tar file, which we named OS39RA.tarz. The z option in the tar command requests compression. The tar/compression step took about 12.6 minutes. The file was saved as a relative name (without the leading /).

2.The ls -alcommand showed the resulting tar file was 468,091,705 bytes. This represents a 6.25:1 compression. Based on PC experience when building AD CD-ROM systems, we typically have approximately a 5:1 compression ratio when compressing files with the zip product for PCs. We have seen ratios from 3:1 to as high as 10:1.

3.We created a new directory, untar, so we could recover the file without destroying the original.

4.We changed to /s390/untar and issued another tar command to extract the file. The additional flags (k w) provided reassurance that we would not overlay our original file. The tar extraction placed the extracted file in the current directory (/s390/untar), but with the additional s390 directory name, and an ls -alcommand confirmed it was the correct size. The tar extraction took about 4.75 minutes.

54S/390 PID: ThinkPad Enabled for S/390