Seperate Java Apps accessing the same table

I have 2 Java applications running independently that will be modifying the same table simultaneously. I am trying prevent the programs from "stepping on each others toes" for lack of a better term. I only want one program to be able to work on this table at a time.
I thought I could somehow use the sql LOCK TABLE command but I wouldn't know how to check to see if a table is locked and prevent one program from proceeding
ie:
While (TABLE IS LOCKED)
//wait
doupdates();
Is there some other mechanism I can use to accomplish this. As I said before, these programs are running independently, the only thing they share is the table they are updating.

Once you execute LOCK TABLE then the table is locked untill you unlock it.
If there was another program which has the lock on the table by the time you invoke LOCK TABLE then the LOCK TABLE call will block until the other program release the lock.
There is no need to check.

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Can ABAP program and a Java apps access the same DB table?

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Hello!
A while ago I was a subject to criticism too for not granting points to helpfull answers. I appeared to be ungratefull, but I'm actually not (I guess the same goes for Vincent). I absolutely agree that good people who provide helpfull answers deserve (at least) points, but I didn't quite get the whole idea with points untill I was explicitly warned. I took some time to correct this and I granted points for all my past questions, generously, with "interest rates" for waiting.
My point is:
The pointing system is good, but unintuitive and not documented. I suggested this at that time, and I see that nothing has changed since. I see also that I'm not the only one who has experienced missunderstandings.
I repeat the message to SDN people: Please provide some info on pointing system! A few sentences behind a "What's this?" link would do. It's not such a hard work.
Thanks!
Kind regards,
Igor Barbaric

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This approach uses the fact, that mutating table problem occurs only with triggers for each row and the order of execution of different trigger types.
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Best regards
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varunsharmaapplefan
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If you havn't done so,you might try the Muse forums and see if you can get a staff member to look into it. Have your case numbers and phone transcripts handy.
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What is the best way to implement this at the application or the database level?
Here are some options we have been bouncing around.
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Thanks

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Hope this helped,
Regards.

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Thanks.

Ricardo_Ruiz_Lopez wrote:
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SSCCE
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C:\Users\Andrew\Hybrid> // YES the previous line requires a '.java' suffix - trust me. ;-)Code
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Edit 1:
Added some access keywords in a passing gesture that the sample aimed at encapsulation.
Edited by: AndrewThompson64 on Sep 2, 2010 1:34 PM

Accessing the same stateful session bean from multiple clients in a clustered environment

I am trying to access the same stateful session bean from multiple
          clients. I also want this bean to have failover support so we want to
          deploy it in a cluster. The following description is how we have tried
          to solve this problem, but it does not seem to be working. Any
          insight would be greatly appreciated!
          I have set up a cluster of three servers. I deployed a stateful
          session bean with in memory replication across the cluster. A client
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          request. Subsequent requests will have to use the same bean and could
          come from various clients. So after using the bean the first client
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          If 'allow-concurrent-call' does exactly what you need, then you don't have a problem,
          do you?
          Except of course if you switch ejb containers. Oh well.
          Mike
          "FBenvadi" <[email protected]> wrote:
          >I've got the same problem.
          >I understand from you that concurrent access to a stateful session bean
          >is
          >not allowed but there is a
          >token is weblogic-ejb-jar.xml that is called 'allow-concurrent-call'
          >that
          >does exactly what I need.
          >What you mean 'you'll get a surprise when you go to production' ?
          >I need to understand becouse I can still change the design.
          >Thanks Francesco
          >[email protected]
          >
          >"Mike Reiche" <[email protected]> wrote in message
          >news:[email protected]...
          >>
          >> Get the fix immediately from BEA and test it. It would be a shame to
          >wait
          >until
          >> December only to get a fix - that doesn't work.
          >>
          >> As for stateful session bean use - just remember that concurrent access
          >to
          >a stateful
          >> session bean is not allowed. Things will work fine until you go to
          >production
          >> and encounter some real load - then you will get a surprise.
          >>
          >> Mike
          >>
          >> [email protected] (Justin Meyer) wrote:
          >> >I just heard back from WebLogic Tech Support and they have confirmed
          >> >that this is a bug. Here is their reply:
          >> >
          >> >There is some problem in failover of stateful session beans when its
          >> >run from a java client.However, it is fixed now.
          >> >
          >> >The fix will be in SP2 which will be out by december.
          >> >
          >> >
          >> >Mike,
          >> >Thanks for your reply. I do infact believe we are correctly using
          >a
          >> >stateful session bean however it may have been misleading from my
          >> >description of the problem. We are not accessing the bean
          >> >concurrently from 2 different clients. The second client will only
          >> >come into play if the first client fails. In this case we want to
          >be
          >> >able to reacquire the handle to our stateful session bean and call
          >it
          >> >from the secondary client.
          >> >
          >> >
          >> >Justin
          >> >
          >> >"Mike Reiche" <[email protected]> wrote in message
          >news:<[email protected]>...
          >> >> You should be using an entity bean, not a stateful session bean
          >for
          >> >this application.
          >> >>
          >> >> A stateful session bean is intended to be keep state (stateful)
          >for
          >> >the duration
          >> >> of a client's session (session).
          >> >>
          >> >> It is not meant to be shared by different clients - in fact, if
          >you
          >> >attempt to
          >> >> access the same stateful session bean concurrently - it will throw
          >> >an exception.
          >> >>
          >> >> We did your little trick (storing/retrieving handle) with a stateful
          >> >session bean
          >> >> on WLS 5.1 - and it did work properly - not as you describe. Our
          >sfsb's
          >> >were not
          >> >> replicated as yours are.
          >> >>
          >> >> Mike
          >> >>
          >> >> [email protected] (Justin Meyer) wrote:
          >> >> >I am trying to access the same stateful session bean from multiple
          >> >> >clients. I also want this bean to have failover support so we want
          >> >to
          >> >> >deploy it in a cluster. The following description is how we have
          >tried
          >> >> >to solve this problem, but it does not seem to be working. Any
          >> >> >insight would be greatly appreciated!
          >> >> >
          >> >> >I have set up a cluster of three servers. I deployed a stateful
          >> >> >session bean with in memory replication across the cluster. A client
          >> >> >obtains a reference to an instance of one of these beans to handle
          >> >a
          >> >> >request. Subsequent requests will have to use the same bean and
          >could
          >> >> >come from various clients. So after using the bean the first client
          >> >> >stores the handle to the bean (actually the replica aware stub)
          >to
          >> >be
          >> >> >used by other clients to be able to obtain the bean. When another
          >> >> >client retrieves the handle gets the replica aware stub and makes
          >> >a
          >> >> >call to the bean the request seems to unpredictably go to any of
          >the
          >> >> >three servers rather than the primary server hosting that bean.
          >If
          >> >the
          >> >> >call goes to the primary server everything seems to work fine the
          >> >> >session data is available and it gets backed up on the secondary
          >> >> >server. If it happens to go to the secondary server a bean that
          >has
          >> >> >the correct session data services the request but gives the error
          >> >> ><Failed to update the secondary copy of a stateful session bean
          >from
          >> >> >home:ejb20-statefulSession-TraderHome>. Then any subsequent requests
          >> >> >to the primary server will not reflect changes made on the secondary
          >> >> >and vice versa. If the request happens to go to the third server
          >that
          >> >> >is not hosting an instance of that bean then the client receives
          >an
          >> >> >error that the bean was not available. From my understanding I
          >thought
          >> >> >the replica aware stub would know which server is the primary host
          >> >for
          >> >> >that bean and send the request there.
          >> >> >
          >> >> >Thanks in advance,
          >> >> >Justin
          >>
          >
          >

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Ok I am going to kick myself for this, but I can't figure it out. I am trying to figure out how to find employees which match multiple criteria in the same table.
create table emp
(empno number,
name varchar2(10))
create table skills
(skill_id   number,
skill_code varchar2(20))
create table emp_skills
(empno    number,
skill_id number,
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insert into emp_skills values(1,3, 10);
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with es1 as(
select s.skill_code, es.empno, es.rating
from skills s, emp_skills es
where s.skill_id = es.skill_id
/* main */
select e.*
from emp e
where
exists
(select 'x' from es1
where es1.rating >= 5
and es1.skill_code = 'SQL'
and es1.empno = e.empno)
and
exists
(select 'x' from es1
where es1.rating >= 6
and es1.skill_code = 'PLSQL'
and es1.empno = e.empno)
and
exists
(select 'x' from es1
where es1.rating >= 7
and es1.skill_code = 'JAVA'
and es1.empno = e.empno)
-- Addition (Another example)
with es1 as(
select s.skill_code, es.empno, es.rating
from skills s, emp_skills es
where s.skill_id = es.skill_id
/* main */
select e.*
from emp e
where
(select count(distinct es1.skill_code) from es1
where
((es1.rating >= 5 and es1.skill_code = 'SQL')
or
(es1.rating >= 6 and es1.skill_code = 'PLSQL')
or
(es1.rating >= 7 and es1.skill_code = 'JAVA')
and es1.empno = e.empno)
=3;

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Hi bucketofsquid -
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Brian Jeffries
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Seperate Java Apps accessing the same table

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