Shell Programming and Scripting

VALUE=`sqlplus un/pwd <<EOF > OB.txt
set pagesize 0 feedback off verify off heading off echo off
select max(1) from table1;
exit;
EOF`

insert into table2 values(1, 'The max value is $value',...);

VALUE=`sqlplus un/pwd <<EOF > OB.txt
set pagesize 0 feedback off verify off heading off echo off
select max(1) from table1;
exit;
EOF`
 
insert into table2 values(1, 'The max value is $value',...); <= at this point, you are out of Oracle, and in the shell. The shell will balk at this SQL statement.

sqlplus un/pwd <<EOF > OB.txt
set pagesize 0 feedback off verify off heading off echo off
declare
  n number;
begin
  select max(1) into n from table1; -- I really don't think you want to fetch "max(1)", which always returns 1. Maybe it's "max(<column_name>)" ?
  insert into table2 values (1, 'The max value is '||n,...);
end;
/
exit;
EOF

sqlplus un/pwd <<EOF > OB.txt
set pagesize 0 feedback off verify off heading off echo off
insert into table2
select 1, 'The max value is '||max(1), ...
from table1;
exit;
EOF