-Netbackup DataCenter 3.4  RMAN 8.1.7.0.0

-problem desc 
-Oracle RMAN backups appear to be slow .......ie
-oracle RMAN jobs submitted for processing small db size 1 - 2 GB takes 24
hours to complete. 

symptoms .... 
-ps -ef  for RMAN process shows 0:00  CPU time on the oracle client,
-job does not show up in Netbackup job monitor ie RMAN is sleeping  
-truss on the RMAN process shows sleeping  .... i.e. .............
aitid(P_ALL, 0, 0xFFBEEC28, WEXITED|WTRAPPED|WSTOPPED) (sleeping...)
-Eventually the job does run to completion ... the concern is that RMAN is
waiting for resources
far too long, and I need to find out what this is .. channel?

log files from RMAN script showing where RMAN is waiting .....this could be 
several hours

 
RMAN-03025: performing implicit partial resync of recovery catalog
RMAN-03023: executing command: partial resync
RMAN-08003: starting partial resync of recovery catalog
RMAN-08005: partial resync complete
RMAN-03023: executing command: backup
RMAN-08008: channel t1: starting full datafile backupset
RMAN-08502: set_count=2188 set_stamp=442232791 creation_time=04-OCT-01
RMAN-08010: channel t1: specifying datafile(s) in backupset
RMAN-08011: including current controlfile in backupset
..........PROCESS sleeping Here ...........
once the resource is available the following line is generated, the job
appears in the
Netbackup job monitor and the job completes within a few minutes.
RMAN-08013 channel T1 piece 1 created 
.... END ........  

Does someone knows where I can get an explanation of RMAN process before it
hands control to NBU , has anyone seen this before, what is the resource
that RMAN is waiting for? 
thanks in advance 
Eustace