Hi Mohd,
You have to increase the Kernel memory for Linux OS.
You have to increase kernel.shmmax parameter in /etc/sysctl.conf.
Then activate changes by running the command 'sysctl -p'.
Also do follow the wiki ERROR shmget ... (28: No space left on device), ERROR semget ... (28: No space left on device) - Basis Corner - SCN Wiki
I don;t think the problem is with SAPUSER table. If the table SAPUSER , is not present then still SAP connect to the Database by using the defaul user from the table DBA_USERS table.Although to make this work , Your SAP and Database will have to be on the same server.
I think , in your landscape you are having the SAP and Database on the same host.If it is distributed , then SAP will not able to connect to Database with the default mechanism.
If you are not in a situation to change the parameter related to OS kernel , then take a reboot of the server which may resolve your issue.
With Regards
Ashutosh Chaturvedi