Oracle Error: Pooled connection request timed out

Question

Im using Oracle12c with the application written in C# and using Oracle.ManagedDataAccess.dll to handle the DB Connection.

A product we have has started to occasionally throw this exception after running fine for years:

Oracle.ManagedDataAccess.Client.OracleException (0xFFFFFC0C): Pooled connection request timed out
   at OracleInternal.ConnectionPool.PoolManager`3.Get(ConnectionString csWithDiffOrNewPwd, Boolean bGetForApp, String affinityInstanceName, Boolean bForceMatch)
   at OracleInternal.ConnectionPool.OraclePoolManager.Get(ConnectionString csWithNewPassword, Boolean bGetForApp, String affinityInstanceName, Boolean bForceMatch)
   at OracleInternal.ConnectionPool.OracleConnectionDispenser`3.Get(ConnectionString cs, PM conPM, ConnectionString pmCS, SecureString securedPassword, SecureString securedProxyPassword)
   at Oracle.ManagedDataAccess.Client.OracleConnection.Open()

I know the cause of this error. Looking at the code neither the OracleConnection or the OracleCommand objects are being disposed. So these connections are building up until it eventually throws this exception.

The fix is straight forward. Wrap these in Using statements. I dont need help with that.

However my interests me is why this problem has started now. This software was running for years without issue. They did some database maintenance, updated other software on the same server, then this problem started. I dont know what Db maintenance they did.

The connection string in the application does not specify any pool attributes.

Is there a oracle db setting which would cause a lower amount of simultaneous connections in the database that could have caused this to start occurring?

UPATE

I wrote a little test app to check the limit. It just loops around and opens a connection, performs a basic query and doesnt dispose the connection. On my test system it starts throwing this exception after 640ish loops. It varies give or take 10 loops each time i run it.

What is setting this limit?

Answer 1

I just had the same problem.

The reason, why you get that exception is, that the Oracle Pool Manager doesn't have a free connection anymore (per default you can have up to 100 connections). Often the reason for that problem are not closed connections (so 'using' was the right ways).

Even though you already found a solid solutions for that problem, I want to add those:

• Try/catch and using is always a good idea
• Adjust the Min Pool Size (or Max Pool Size, but default is 100 should be enough): So there's always a connection ready to use and the connection doesn't have to get established (see https://docs.oracle.com/en/database/oracle/oracle-database/21/jjucp/optimizing-ucp-behavior.html#GUID-FFCAB66D-45B3-4D7B-991B-40F1480630FD )
• Update to Oracle.ManagedDataAcess >= 21.8.0 ( Bug 34322469 - CONNECTION POOL THROWS "CONNECTION REQUEST TIMED OUT" EXCEPTION DUE TO LOOPING WITHIN POOLMANAGER.GET() is fixed there)