Problems with Large XDB or OP2

If you are constantly having to work with large models and larger output in XDB format, MSC Nastran has come out with a good solution. A common fatal message encoutered while writting out large size xdb files is UFM 6062(DBC). There are standard solutions available to avoid this fatal message. However, by including the following in NASTRAN SYSTEM CELL and FMS, I have been able to run models and output upto 40GB of xdb file:
  1. Insert in NASTRAN SYSTEM CELL – NASTRAN DBCFACT=4
  2. Insert in FMS – ASSIGN DBC=’filename.xdb’,RECL=32768,UNIT=40,DELETE
NASTRAN DBCFACT=4 is a new command introduced from MSC Nastran 2005 + versions. This command creates a new format of xdb file and supports the creation of virtually unlimited size of xdb.
Example Input:
$ Direct Text Input for Nastran System Cell Section
NASTRAN SYSTEM(151)=1
NASTRAN BUFFSIZE=65537
NASTRAN DBCFACT=4
$ Direct Text Input for File Management Section
ASSIGN DBC=’nl_150bar.xdb’,RECL=32768,UNIT=40,DELETE
$ Nonlinear Static Analysis, Database
SOL 106
$ Direct Text Input for Executive Control
CEND

 

This procedure could be used also for OP2 file results. Another way to get rid this problem is to use the keyword “memory”. Below is described in detail how to use it.

 

  • Memory

This keyword is used to specify the amount of memory to allocate. If this parameter is not specified, than the default amount is used (pre-setting in the RC file for exemple). The memory amount can be specified in terms of  number of “words” or byte (sometimes can be specified in the .dat or .bdf file by BUFFSIZE as well) contained in the phisical record.

Exempes:

  nastran2012  job.dat  memory=25mw

The job is run using an open core memory size of 25 megawords, or 25600 kilowords (25×1024, 25600kw), or 26 214 400 words (25x1024x1024). Instead of “mw” can be used “m” as well.

  nastran2012  job.dat  memory=25mb

The job is run using an open core memory size of 25 megabytes, or 25600 kilobytes (25×1024, 25600kb), or 26 214 400 bytes (25x1024x1024). The number of bytes is 8 for operative system like Unix (CRAY UNICOS, NEC), and 4 on all others.

  nastran2012  job.dat  memory=25gb

The job is run using an open core memory size of 25 gigabytes, or 25600 megabytes (25×1024, 25600mb), or 26 214 400 kilobytes (25x1024x1024). With “w” it is possible to use the memory size as is.

 

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