How to use the TIMESTAMP_TO_SCN function

select timestamp_to_scn(to_timestamp('2020-05-11 14:36:22', 'YYYY-MM-DD HH24:MI:SS')) "scn" from dual;

scn
----------
20325895

Reversed:

select scn_to_timestamp(20325895) "timestamp" from dual;

timestamp
----------------------------------
11-MAY-20 02.36.20.000000000 PM

How to avoid the error Can't locate Data/Dumper.pm in @INC during installation of AHF

During installation of ahf, I received the following error:

Extracting AHF to /u01/ahf/oracle.ahf
Can't locate Data/Dumper.pm in @INC (@INC contains: /usr/local/lib64/perl5 /usr/local/share/perl5 /usr/lib64/perl5/vendor_perl /usr/share/perl5/vendor_per l /usr/lib64/perl5 /usr/share/perl5 . /u01/ahf/oracle.ahf/tfa/bin /u01/ahf/oracle.ahf/tfa/bin/common /u01/ahf/oracle.ahf/tfa/bin/modules /u01/ahf/oracle.a hf/tfa/bin/common/exceptions) at /u01/ahf/oracle.ahf/tfa/bin/common/tfactlshare.pm line 1350, line 1.
BEGIN failed--compilation aborted at /u01/ahf/oracle.ahf/tfa/bin/common/tfactlshare.pm line 1350, line 1.
Compilation failed in require at /u01/ahf/oracle.ahf/tfa/bin/tfasetup.pl line 107, line 1.
BEGIN failed--compilation aborted at /u01/ahf/oracle.ahf/tfa/bin/tfasetup.pl line 107, line 1.

Solution: Install missing packages:

su -
yum install perl-Data-Dumper

At this point, you need to uninstall AHF:

tfactl uninstall

Then cleanup old files. Go to the directory where you attempted to install AHF;

cd /u01/tfa
rm -rf oracle.ahf

Go to the directory where the zipped file has been extracted, and run the installation again:

/u01/oracle/patch/AHF
./ahf_setup