groupadd --gid 54321 oinstall;
groupadd --gid 54322 dba;
groupadd --gid 54323 asmdba;
groupadd --gid 54324 asmoper;
groupadd --gid 54325 asmadmin;
groupadd --gid 54326 oper;
groupadd --gid 54327 backupdba;
groupadd --gid 54328 dgdba;
groupadd --gid 54329 kmdba;
useradd --uid 54321 --gid oinstall --groups 'dba,oper,asmdba,asmoper,backupdba,dgdba,kmdba' oracle;
useradd --uid 54322 --gid oinstall --groups 'dba,asmadmin,asmdba,asmoper' grid;
## set default passwords for these users?
echo  -e "aNYlbpdQKzBacjOg" | (passwd --stdin grid)
echo  -e "aNYlbpdQKzBacjOg" | (passwd --stdin oracle)

On Linux, Automatic Storage Management uses asynchronous Input-Output by default.
if database files are not on asm:

alter system set filesystemio_options=asynch scope=spfile;
alter system set disk_asynch_io=true scope=spfile; 

save a lot of time later, need for logminer:

ALTER DATABASE ADD SUPPLEMENTAL LOG DATA; 
ALTER DATABASE ADD SUPPLEMENTAL LOG DATA (PRIMARY KEY) COLUMNS; 

alter system set resumable_timeout=3600;
alter system set ddl_lock_timeout=60;

setup awr snapshot retention:

in case with ADG: Installing and Using Standby Statspack in 11g (Doc ID 454848.1)