Tim,
I order the Oracle 8.1.7 for Solaris Intel from Oracle.

Sam,

Thaks again. Let me tell you the whole story. After installation the Oracle product, the Installer continous to did the option step, the first one is the Net8 Configuration Assistant it complete success. the 2nd step is the Data Base Configuration Assistant it did not success due to Oracle Not Available. But Oracle sad this is the Optional Step. So I went into the Oracle use the svrmgrl to connect to oracle as Internal/Oracle then I run Startup nomount, it success, then I open another terminal and run the dbassist to create the database the global data base name is "world" , SID is "orcl" then the database created success. then I check into the oracle/admin/pfile,/udump, /cdump and oradata all the control file is created and also initorcl.ora is created in the /pfile but in there are 3 control files in the /oradata names as control01.ctl, control02.ctl and control03.ctl. Right now the interesting thing happend, if I use Startup nomount pfile=the initorcl.ora in the pfile folder then I got end-file-file communication chanell error, but if I use Starup nomount and I do not specific which init .ora file, it success and I can continue ALTER DATABASE OPEN, then I run the Show Parameter and v$parameter I found the control_files is not the 3 controlfiles as I mention before, it is another 2 controlfiles, they are in the /u02/oradata and then I found out these 2 control_files specific from another initorcl.ora this init is in the /u01/app/oracle/product/8.1.7/dbs/initorcl.ora, this file is little difference from the other initorcl.ora, it only contains the db_name=orcl, but no instance_name and service_name entry and also before it can not MOUNT the database, until I change the db_name=orcl to db_name=world. and I also run the ALTER DATABASE BACKUP CONTROFILES TO TRACE so I verify the contents in the trace file, I found the LOG FILE, DATA FILE all in the /oradata/world, but it did not use the initorcl.ora in the world/pfile, that is the whole story.
Let me answer your question, 1. env show the ORACLE_SID=orcl, 2. the oratab not exist in the var/opt/oracle, so I did not know how many instances. 3. when I run dbassist again the Modify and Delete are disable, it means there is not any database available for Modify and Delete only the create database option is enable, I think it is rare. But it is very interesting I can use sqlplus or svrmgrl to do everything. I still do not know why I can not specific the initoracl.ora in the world/pfile and also use the control files specific in the pfile/initorcl.ora and also get error, but if I do not specific the initorcl.ora it automatic use the one in the oracle/product/8.1.7/dbs and use another set control files and also very funny I only got a set of DATA FILES and LOG FILES.
and why that dbs/initorcl.ora do not include the instance_name and the service_name. but the other had instance_name=orcl and service_name=world.

May be I want to rename the pfile/initorcl.ora to pfile/initworld.ora and change the ORACLE_SID in the env from ORACLE_SID=orcl to ORACLE_SID=world. What you think, it is will fix that funny problem?

Thank you very much for your advise.