You need to search for OWNER_NAME.
cat -v dumpfile.dmp | grep -o '<OWNER_NAME>.*</OWNER_NAME>' | uniq -u
cat -v turn the dumpfile into visible text.
grep -o shows only the match so we don't see really long lines
uniq -u removes duplicate lines so you see less output.
This works pretty well, even on large dump files, and could be tweaked for usage in a script.