2522191 - Instance does not appear in SM51, SAP processes are hanging, traces cannot be read

• Dispatcher, work processes are hanging
• SM51: instance doesn't appear there
• ls -al /usr/sap/SID/instance/work command just hanging
• dev_disp cannot be opened
• sapstack <PID> command cannot debug the process, just hanging
• operating system debug tools (e.g. GDB) cannot debug the process, just hanging
• in dmesg similar entries may appear like
   
  [36721.049838] [<ffffffffa0779fb0>] ? nfs4_xdr_dec_access+0xc0/0xc0 [nfsv4]
  [36721.049844] [<ffffffffa077a040>] ? nfs4_xdr_dec_getattr+0x90/0xa0 [nfsv4]
   
  [410068.065140] nfs: server <server name> not responding, still trying
   
• df /usr/sap/SID/instance/work 
  and|or
  df /usr/sap/SID/instance/exe points to <server name> above, e.g.:
   
  df /usr/sap/SID/D04/work
  Filesystem 1K-blocks Used Available Use% Mounted on
  <server name>:/usr/sap/SID 25672704 6608896 17753088 28% /usr/sap/SID
   
  df /usr/sap/SID/D04/exe
  Filesystem 1K-blocks Used Available Use% Mounted on
  <server name>:/usr/sap/SID 25672704 6608896 17753088 28% /usr/sap/SID

SAP on UNIX, Linux operating system

hanging, NFS, NFSv3, NFSv4, dbg, gdb, local, sapstack , KBA , BC-OP-LNX , Linux , BC-CST , Client/Server Technology , BC-CST-DP , Dispatcher, Task Handler , BC-OP-AIX , IBM AIX , BC-OP-HPX , HP-UX , BC-OP-SUN , SUN Solaris , Problem