NDMP Backup Job fails with a 'Failed to build index' error message. (4037360)

NDMP Backup Job fails with a 'Failed to build index' error message.

The Binary log shows the following errors and messages:

1] Background   2014/11/29 03:16:16   40   Data Plugin   tractor.org.aalto.fi   Index names
2] Information   2014/11/29 03:16:16   40   Data Plugin   tractor.org.aalto.fi   Using 32342Kb of memory for directory map
3] Error   2014/11/29 03:17:06   40   Data Plugin   tractor.org.aalto.fi   Failed to build index

With sub text:
RECS       47       0  31706 RecsClose: start processing (0x1bdbf80, /l/netvault/tmp/00225002250000000002)
RECS       48       0  31706 RecsClose: closing (0x1bdbf80, /l/netvault/tmp/00225002250000000002)
FILE        2       0  31706 FileDelete("/l/netvault/tmp/00225002250000000002")
FILE        2       0  31706 FileDelete("/l/netvault/tmp/00225002250000000008")
NDMPBACK  207       0  31706 Failed to build index

4] Job Message   2014/11/29 03:17:06   40   Media   tractor.org.aalto.fi   Device 'SmartDisk - localhost' has completed its transfer
5] Information   2014/11/29 03:17:06   0   Data Plugin   tractor.org.aalto.fi   RAS transfer has been ended for device connection
6] Error   2014/11/29 03:17:06   40   Jobs   tractor.org.aalto.fi   Job Status: Backup Failed

As per the following KBA, there was enough free space on the NetVault Server tmp folder to create the Index i.e. 82GB free disk space:

https://support.quest.com/netvault-backup/kb/81102

The following KBA for the same error message made no difference either:

https://support.quest.com/netvault-backup/kb/127875

The NDMP trace files showed the following error messages:

0 FILESYS :10567 19 24 031705.761085 Failed to open /l/netvault/tmp/00225002250000000002 error Too many open files
0 NDMPBACK:10567 214 0 031705.761097 Failed to reopen Directories file with 56 byte buffer
1 NDMPBACK:10567 207 0 031706.080559 Failed to build index

Increasing the maximum number of open files is OS dependent.

For most Linux releases, increase the "nofiles" (or "open files") value by "ulimit -n xxxx (where xxxx is a number)" or "ulimit -n unlimited".
Place the command in NetVault startup.sh script or reconfigure the global user limits, then restart NetVault service (or Operating System) accordingly.
Unlimited is the best option.
Further information is in the following KBA:

https://support.quest.com/netvault-backup/kb/79736

This can also be read in section 3.2.1 under the 'Configure “ulimit” Variables (Linux/UNIX Platforms Only)' item of the NVBU 9.2 Installation Guide on the following link:

https://support.quest.com/netvault-backup/technical-documents