Connection pool has been unable to grant a connection to thread
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I'm using GreenDAO for database handling in Android. When performing many database changes (> 15.000) I get this error Message:

"The connection pool for database '/data/data/...' has been unable to grant a connection to thread 312 (Thread-312) with flags 0x1 for 30.000002 seconds."

Everything gets stuck. Why does this error happen?