Table of Contents
cat.compare
Overview
Developers frequently need to compare two clusters. Determining the differences between them visually is too error-prone and because the files reside in containers, normal comparison tools are not available. During the catalog process, a cryptographic signature is taken of the contents of each file and these signatures may be used to perform a very fast comparison of the contents of two clusters.
The COMPARE Operation
Listing the catalog's primary contents tells us the clusters available for comparison:
Our task is to determine how far cluster βNCC.CybisRelease1β has deviated from the baseline βTH.CybisRelease1β.
We invoke the cat.compare
subcommand and the following is displayed in less than a second (on most systems):
29 Differences were found.
Analyzing the Output
Just because two files differ doesn't tell us enough. Unless we specifically understand the contents of the file in question, βbeing differentβ doesn't indicate whether the differences are desireable or not.
In the list above, item 0 a0aids1 contains different block types:
source
common
llist
text
Commons can be very volatile and may be the reason for the discrepancy between the two clusters.
In this case inspecting the LAST EDITED
dates of the blocks may be more informative.
Likewise, other files can be quite volatile, especially system files such as:
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Therefore, process of elimination tells us that the most likely changes between these two systems were the files not present on the TH.CybisRelease1, added to the NCC.CybisRelease1 distribution:
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Other Information
The report also provides side-by-side comparison between the corresponding files and attempts to make
recommendations regarding the possibility of copying the file using cdc.io
.
Attributes Displayed
- PLATO File Type
- Account of Residence
- Number of BLOCKS 2) allocated to the file.
- Masterfile (NOS File) of residence
See the article Copy Modes for guidance regarding the dangers of copying to a live system.
Success
Congratulations!
You have now successfully compared the contents of two clusters!