NX Nastran - extreme size of SCR300

[mbiskup]

Hi,
I have issue witn NX NAstran 8.5.
We have changed MSC.Nastran to NX Nastran 8.5 and now I am not able to perform larger analysis.
I am running harmonic anlysis and almost all jobs a finishing with following message:

*** USER FATAL MESSAGE 1012 (GALLOC)
DBSET SCRATCH IS FULL AND NEEDS TO BE EXPANDED.
USER ACTION: SEE THE NX NASTRAN INSTALLATION AND OPERATIONS GUIDE OR
TAN 4893 ON THE UGS WEB SITE FOR METHODS TO MAKE LARGER DATABASES.
BIOMSG: ERROR 4276 HAS OCCURRED IN ROUTINE GALLOC , FILE INDEX = 0.
STATUS = 0
I have checked size of the SCR300 and it was growing to maximal full disc space (650 GB).
MSC Nastran required overall disc (results and scratch) space only about 100 GB.
I have also tried to use options SSCR=240GB, SDBALL=240GB, but without results. Please can somebody help me?
Thak you in advance.
Martin

 

[BlasMolero]

Dear Martin,
Then check the Nastran output request ítems, activate the mínimum output you need, like Displacements & Stress.

Also, check the nastran/conf directoy, and there the nast8.rcf file, check that su have defined properly the value of SDIR , MEM and buffsize. For big models I suggest to use
Buffsize=65537. Also set the amount of RAM memory to assign to nastran solver by MEM=xxGB

Is imposible that the same model in msc nastran requires 100 Gb for solving and using NX Nastran you need 650 GB ...

Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48011 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

http://iberisa.wordpress.com/

 

[mbiskup]

Dear Blas,
we have also discuss it with the vendor and he told us to add new parameters (not used in MSC Nastran) and it looks it works. The SCR300 was now maximal 30GB. The parameters were automatically generated by NX.
I like to know what they mean (I don't like black box

PARAM OMACHPR YES
PARAM POSTEXT YES
PARAM DDRMM -1
I have one more question related to RAM definition. We have issue on the Windows platforms. It looks the Nastran ignore it and use whole RAM. How it should be defined properly.
Thank you very much.
Martin

 

[BlasMolero]

Dear Martin,
This is more reasonable. The keypoint here is DDRMM parameter (Dynamic Data Recovery Matrix Method). In the case of dynamic analysis with the modal formulation, two methods of data recovery are available. The default procedure is usually much more efficient for data recovery operations when the modal formulation is used for dynamic analysis. In this procedure, the dependent components of the eigenvectors used in the modal formulation are first recovered by SDR1 using the same sequence of operations described for problems in real eigenvalue analysis (after eliminating unwanted modes). The complete eigenvectors are used as the input to SDR2 in order to determine the requested forces and stresses in terms of modal coordinates.

In dynamic analysis, you may restrict the output request to the response of selected points in the solution set. In this case, the time-consuming operations in the recovery of the dependent degrees-of-freedom can be avoided. This solution set processing is performed by VDR (Vector Data Recovery).

The modal data generated by SDR1 and SDR2 are formed into a data matrix by DDRMM. The output quantities are determined by multiplying the data matrix by the modal solution vectors. The computer time for this matrix multiplication is proportional to the number of output times, the number of modes used in the modal formulation, and the number of output frequencies or output time steps. If both the number of output items and the number of modes are small, the computer time required will not be significant when compared to the total problem solution time. Although the DDRMM method of data recovery is more efficient, a complete {ug} is not formed. For this reason the method does not permit the creation of deformed structure plots, grid point force balance or the use of the mode acceleration technique.

The alternate procedure may be invoked using PARAM,DDRMM,-1. With this method the solution vectors are first transformed from modal to physical coordinates. PARAM,DDRMM,-1 and PARAM,CURVPLOT,1 are required in the Bulk Data to create structure plots at specified frequencies. (Note that PARAM,DDRMM,-1 generally increases the amount of computer time and is not recommended unless otherwise required.)

Regarding RAM performance, I have learned from NX NASTRAN developers that Nastran is very much file based and IO performance is almost always the limiting performance factor. Hardware money is much better spent on disk striping (i.e. RAID 0, modern fast SSD) rather than multiple processors. Additional memory helps to some extent as the modern operating systems (Windows and Linux) use unallocated RAM as IO cache.

This point is critical: all of the unallocated RAM is used by the OS as cache to help IO. If you take a look to the TASK MANAGER you will see that NX NASTRAN use the RAM memory you assigned by MEM command, ie, if you set MEM=5GB then NX NASTRAN will use 5 GB RAM as maximum, the rest of RAM will be used by the OS as IO cache, OK?.

Then, if in a dynamic response analysis you get any message in the output file *.F06 like:

AVAILABLE MEMORY IS LESS THAN THE MEMORY NEEDED TO HOLD
LOADS AT DIFFERENT FRQUENCIES/TIMES INTERVALS. THIS WILL
IMPACT PEFORMANCE AS SPILL LOGIC WILL BE USED. PLEASE
INCREASE MEMORY BY     xxxxxxx WORDS TO HOLD THE LOADS INCORE

then simply increase the RAM memory devoted to the solver. If the NX NASTRAN solver ask more than 8 GB RAM, then you will need to use the ILP-x64 NX NASTRAN solver (with 8 bytes per word) instead the regular LP-64 solver (by default).

Best regards,
Blas.




~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48011 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

http://iberisa.wordpress.com/

 

[mbiskup]

Dear Blas,
thank you very much for your answer.

I will tell my boss I need new computer .
Have you nice day
Martin