Mechanical APDL Basic Analysis Guide

7.1.2.1. Defining Data to be Retrieved

The INRES command (Main Menu> General Postproc> Data & File Opts) in POST1 is a companion
to the OUTRES command in the PREP7 and SOLUTION processors. Where the OUTRES command controls
data written to the database and the results file, the INRES command defines the type of data to be
retrieved from the results file for placement into the database through commands such as SET,SUBSET,
and APPEND. Although not required for postprocessing of data, the INRES command limits the amount
of data retrieved and written to the database. As a result, postprocessing your data may take less time.

7.1.2.2. Reading Selected Results Information

To read a data set from the results file into the database for the selected portions of the model only,
use the SUBSET command (Main Menu> General Postproc> Read Results> By characteristic).
Data that has not been specified for retrieval from the results file by the INRES command will be listed
as having a zero value.

The SUBSET command behaves like the SET command except that it retrieves data for the selected
portions of the model only. It is very convenient to use the SUBSET command to look at the results
data for a portion of the model. For example, if you are interested only in surface results, you can easily
select the exterior nodes and elements, and then use SUBSET to retrieve results data for just those se-
lected items.

7.1.2.3. Appending Data to the Database

Each time you use SET,SUBSET, or their GUI equivalents, the program writes a new set of data over
the data currently in the database. The APPEND command (Main Menu> General Postproc> Read
Results> By characteristic) reads a data set from the results file and merges it with the existing
data in the database, for the selected model only. The existing database is not zeroed (or overwritten in
total), allowing the requested results data to be merged into the database.

You can use any of the commands SET,SUBSET, or APPEND to read data from the results file into the
database. The only difference between the commands or paths is how much or what type of data you
wish to retrieve. When appending data, be very careful not to generat e a data mismatch inadvertently.
For example, consider the following set of commands:

/POST1

INRES,NSOL! Flag data from nodal DOF solution

NSEL,S,NODE,,1,5! Select nodes 1 to 5

SUBSET,1! Write data from load step 1 to database

At this point results data for nodes 1 to 5 from load step 1 are in the database.

NSEL,S,NODE,,6,10! Select nodes 6 to 10

APPEND,2! Merge data from load step 2 into database

NSEL,S,NODE,,1,10! Select nodes 1 to 10

PRNSOL,DOF! Print nodal DOF solution results

The database now contains data for both load steps 1 and 2.This is a data mismatch. When you issue
the PRNSOL command (Main Menu> General Postproc> List Results> Nodal Solution), the program
informs you that you will have data from the second load step, when actually data from two different
load steps now exist in the database. The load step listed by the program is merely the one corresponding
to the most recent load step stored. Of course, appending data to the database is very helpful if you
wish to compare results from different load steps, but if you purposely intend to mix data, it is extremely
important to keep track of the source of the data appended.

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Reading Results Data into the Database