One of our customer need to decreased server RAM from 128Gb to 32 Gb.

After closing database, We rebooted server. While server trying to open it gave below error message:

Here is the solution for this error:

1. Check below files for hugepages config

cat /etc/sysctl.conf |grep -i huge
vm.nr_hugepages = 38903

cat /etc/sysctl.d/99-initial-sysctl.conf |grep -i huge vm.nr_hugepages = 5000

cat /etc/sysctl.d/99-oracle-rdbms-server-12cR1-preinstall-sysctl.conf |grep -i huge vm.nr_hugepages = 5000

Found these miss-configuration from the data collected

2. Update/Edit files and set the kernel parameter value “same” everywhere.
3. Reboot server

References:
HugePages Not Getting Allocated Correctly After Server Reboot (Doc ID 2610185.1)
Server Hung During Boot With Error ‘/etc/initd/functions: fork: Cannot allocate memory’ (Doc ID 2276510.1)
How to Collect sosreport under Rescue Mode (Doc ID 1928852.1)