OracleDataSource Connection is null after using it 4 times - oracle

Question

I am trying to use an OracleDataSource connection more than once. In the class, I have set the cacheProperty to 10:
cacheProps.setProperty("MaxLimit", "10");
The class that calls the connection is waiting for a return value so that both calls are not being made at the same time. The class that uses the connection is getting a null pointer with the connection variable at random places in the class. It always happens on the 5th request. Is there some property that I'm unaware of that implies you can only use a connection pool 4 times?
This is the code snippet where the null pointer occurs:
int threadNo = 2;
Connection conn = OraConnODS.getConnection("env " + threadNo);
conn.setAutoCommit(false);
Statement stm = conn.createStatement();
Usually on the second line, and sometimes on the third.

Answer 1

try this query to check how many connections are actually open in oracle
SELECT
'Currently, '
|| (SELECT COUNT(*) FROM V$SESSION)
|| ' out of '
|| VP.VALUE
|| ' connections are used.' AS USAGE_MESSAGE
FROM
V$PARAMETER VP
WHERE VP.NAME = 'sessions'
and see if the count is > 10. If > 10 then you need to post your full code/xml to let us have a look at.

Answer 2

First of all you should try using DB conection pool like C3P0 rather than using datasource directly. This way you will have more control over it.
Anyway, your problem seems to be relation Connection leaks. There might be some stale connections lying around which prevent you from creating more connections. SO next step will be to check how many conections are open [see satya's answer for it]. But then next issue will be to remove stale conections tht will be tough, so i would again suggest DB connection pool.
EDIT: Ok, i can see that you are using connection pool, then try to print total active connections and you will be able to reach the root issue. I faced same issue due to connection leak and crude fix will be to clean connection with brute force [generally Connection pools provide such api, atleast C3P0 does]. Get connection pool log and you will know root cause.