What might be the cause and solution to this error:

Code:
05.May.15 15:30:00,151 <ERROR> Unable to open Audit file in append mode.: {}.                                                
java.io.FileNotFoundException: /RNS/lightstreamer/conf/./../audit/audit_log_b2-d3-5d-1a-b2-04_28.txt (Too many open files)   
 at java.io.FileOutputStream.<init>(FileOutputStream.java:231) ~[na:1.7.0]                                                   
 at java.io.FileWriter.<init>(FileWriter.java:118) ~[na:1.7.0]                                                               
 at com.lightstreamer.j.d.a(d.java) [lightstreamer.jar:na]                                                                   
 at com.lightstreamer.j.d.a(d.java) [lightstreamer.jar:na]                                                                   
 at com.lightstreamer.j.d.a(d.java) [lightstreamer.jar:na]                                                                   
 at com.lightstreamer.j.a.run(a.java) [lightstreamer.jar:na]                                                                 
 at java.util.TimerThread.mainLoop(Timer.java:566) [na:1.7.0]                                                                
 at java.util.TimerThread.run(Timer.java:516) [na:1.7.0]