Backup database and archivelog by Rman with catalog then ORA-03114: not connected to ORACLE

 hello,       I execute my backup with RMAN with Catalog by netbackup V6.5. on a server linux Readhat.
      The script are working on others system except in linux.
      I would like trace the all process to understand my error and find a process of workaround. 

      For me : I think I losed the connection with RMAN and RCAT, but I Do not understand why ?
    
My error is : ORACLE error from recovery catalog database: ORA-03114: not connected to ORACLE
released channel: ch00
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of sql command at 05/12/2011 23:50:18
RMAN-06004: ORACLE error from recovery catalog database: ORA-03114: not connected to ORACLE