Critical section with Sql*Load

Question

Hi,
I need to prevent multiple instances of a batch job from running at the same time. This is easy when the batch job is pure PL/SQL. A critical section implemented with DBMS_LOCK does the job just well.
But now I have a batch job which first uploads a file using Sql*Load, and only later calls Sql*Plus and PL/SQL.
How do I prevent multiple instances of my Sql*Load from running in parallel ? (i.e. writing into the same table).
I've heard about restricting the number of concurrent sessions in the login profile. Trouble is, I have a dozen different "types" of batch jobs, and we don't want to have a dozen different logins. Batches of different types are allowed to run in parallel, and this is even desirable.
Andrew

Answer 1

Since sqlldr is essentially an O/S command, you will need to do the locking at the O/S level. Depending on how you call the batch jobs, you have two choices.
If the controlling script and/or the loader control file for each batch have a consistent name, then you can do something like:
#!/usr/bin/ksh
me=$$
while [ $me -ne 0 ]
do
   run=`ps -ef |grep <<script_or_control_file_name>> |grep -v grep |grep -v $me`
   if [ "$run" = "" ]; then
      run sqlldr and
      rest of batch commands
      break
   else
     sleep or exit or whatever
   fi
done
-- Any post processing requiredWe have situations where the controlling shell script, and the loader control file are automatically created by a master control program. Since the file names differ for every run, we use a structure like this:
#!/usr/bin/ksh
flagfile=batch1.flg
while [ $flagfile = $flagfile ]
do
     if [ ! -f $flagfile ]; then
        touch $flagfile
        run sqlldr and
        rest of batch commands
        if [ successful ] ; then
           rm $flagfile
        fi
        break
     else
        sleep or exit or whatever
     fi
done
-- Any post processing requiredHTH
John