We're running an enterprise scale SAP application with front-end springboot clients connecting via Jco adapter 3.0 on Oracle VM using the connection pool (size 100). We're experiencing unsystematic long-running requests > 10s that are not visible in the SAP application server log, i.e. the bottleneck does not appear to be on SAP side.

Looking at the trace files (level 4) for an example request we can see that the time seems lost when the adapter thread tries to get the client from the pool (other threads continue execution, removed the irrelevant threads for clarity):

```
[20:05:50:259]: [JCoAPI] JCoContext.isStateful(P-foo-CPIC0) in session ID Client-53-1 returns false
[20:05:50:259]: [JCoAPI] JCoContext.begin(P-foo-CPIC0) in session ID Client-53-1
[20:05:50:259]: [JCoAPI] Started context for session Client-53-1
[20:05:50:259]: [JCoAPI] JCoContext.begin() for destination PFOO_200 (P-foo-CPIC0) on context with id Client-53-1; current state counter is 1
[20:05:50:259]: [JCoAPI] destination PFOO_200 destinationID=P-foo-CPIC0 executes Z_foo sessionID=Client-53-1, threadID=0x35
[20:05:50:259]: [JCoAPI] Context.getConnection on destination PFOO_200 (state: destination = STATEFUL, default = STATELESS)
[20:05:50:259]: [JCoAPI] PoolingFactory.getClient() on pool P-foo-CPIC0
--> time lost here
[20:06:20:840]: [JCoAPI] PoolingFactory.getClient() returns handle [3/84977415]
[20:06:20:840]: [JCoAPI] Context.getConnection on destination PFOO_200 nothing found in the context - got client from ConnectionManager [3/84977415]
[20:06:20:840]: [JCoAPI] JCoClient before execute(Z_foo) on handle [3/84977415]
[20:06:20:840]: [JCoRFC] Executing function Z_foo on handle [3/84977415]
[20:06:20:866]: [JCoAPI] JCoClient after execute(Z_foo) on handle [3/84977415] returns after 26 ms
[20:06:20:866]: [JCoAPI] Context.releaseConnection on destination PFOO_200 [3/84977415]
[20:06:20:867]: [JCoAPI] JCoContext.end(P-foo-CPIC0) in session ID Client-53-1
[20:06:20:867]: [JCoAPI] PoolingFactory.releaseClient() handle [3/84977415] into pool P-foo-CPIC0 [pool size: 3, peak limit: 100, waiting threads: 0, currently used: 1]
[20:06:20:879]: [JCoAPI] Finished context for session Client-53-1
[20:06:20:879]: [JCoAPI] JCoContext.end() for destination PFOO_200 (P-foo-CPIC0) on context with id Client-53-1; current state counter is 0

```

For a typical request the step is handled in milliseconds.

Are there any known limitations or configurations regarding pool handling for the Jco adapter, either on adapter or on SAP side?

**Update** we've on Jco adapter `3.0.16` and will double-check `3.0.17` now. DNS seems unlikely since we're monitoring `dig`/`nslookup` and they're running without delays.