Global variable, memory

Hi,
I am using global variables in order to share values captured by one VI (as kind of data source) with other VIs, but after several days of continuous running I recieve Error 2:Memory is full.\
Please advise how can i empty global variables or use other way of sharing data between VIs continuously without interruptions.
Thanks

Innka wrote:
I am reading and sharing values from indicators which are communicating using .NET protocol, and the values are received as two signed 6 digit numbers (DBL) and I am sampling the data every second. The idea was replacing the value each second and not creating the array of values.
So you don't have an array? The the global variable is not your problem. The .NET interface could be something to look at. Are you opening a .NET interface inside of a loop without closing it?
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
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Similar Messages

Function module Global variables not cleared from memory?

Hi,
This is may be simple & stupid question ( after posting 4242 posts ):)
" Declaration in TOP
data : begin of i_y1yatt occurs 0.
        include structure y1yatt.
data : end of i_y1yatt.
types: begin of t_yatt71.
       include structure yatt71.
types: tcode like sy-tcode.
types: dflag type c.
types: end of t_yatt71.
data : i_yatt71 type standard table of t_yatt71
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This is code in the function module.
loop at i_y1yatt.
    move-corresponding o_y1yatt to i_yatt71.
    if i_y1yatt-werks eq 'N501'.
       move space to i_yatt71-werks.
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    append i_yatt71.
    " Here this internal contains the previous entry
    clear i_yatt71.
endloop.
This function module is called 25 times in a minute.
My problem is this
For example : 1st tranmission is called this fm with 50 records,
and 2nd tranmission is called fm with 10 records.
My results are showing
last record in the 1st transmission is still on the memory while calling 2nd transmission. ( Here in int table I_YATT71 still contains the 1st transmission's last records during the 2nd tranmission call)
As per my knowledge if each time calls comes in to fm all gloabl variables get cleared. but some how this not happening.
Anybody come across this scenario.
PS. I know i need to use clear statement within the loop as first statement.
a®

You must understand that when calling a FM, you load the entire function group into memory. IF there are global variables, then they are "alive" for the entire duration of the program execution. Meaning if you call the function numerious times, or even if you call another function within the same function group, the functions still have access to that same global variable space, so it must always be cleared manually by the developer at the required points. You can not rely on the runtime to clear the global variables at the end of the function call. So you should clear all you globals as the first operation in your function module call, if that is what is required.
Is this clear?
Regards,
Rich Heilman

Need features of global variables but want to avoid re-writing to memory

I am making a program with a number of simultaneous loops that will be sharing several variables. Most of the variables are of size 1 or small arrays, so I am not too concerned about the constant re-writings involved. However, I have one rather large data buffer (3D array containing 200Kb+ of data). The buffer will be of a set size. In the various loops, the buffer will be accessed for updates (generally with Replace Array subset), and read from to get average values and such. I'm using semaphores so that none of the loops interact negatively and lose data. In other programs I'd set this up with a shift register in the loop, but since the data is being used in separate simultaneous loops, it's no
t really possible to wire it up that way. I need some sort of memory-space that can be accessed from the various loops.
I guess in sorts, I need to be able to have global variable 'pointers', but of course I was told a couple of years ago at a LabView seminar that pointers was a bad word.

tbob wrote:
> As long as Labview is running, the LV2 style global will automatically
> retain its last value. Of course the very first time it is run, the
> value is undefined, so you should write to it before attempting any
> read.
I have one correction to make. The value of an unitialized shift
register on first load is not undefined but rather contains the
datatype's default default value. This would be False for booleans, 0
for numerics and empty arrays or strings.
Rolf Kalbermatter
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

Import/export to memory and global variables

Hi,
Im working on some functionality using import/export to memory. One of the statements is:
import gf_memid_exit = g_exit_flag gf_memid_result = t352r from memory id 'ZREV_EXT'.
Im using global variables to contain the cluster names. But this is not working. When I change the global variables into local variables, it works. It this normal? Because I would like to have global variables (even better I would like to have global constants) to declare in order to use them within the program.
Any ideas?
With regards,
Mike

Hi Mike...
I think with import u can use global or local variables..in debug mode pl. check when u r using global variables..whether it is getting cleared or overwritten by some other values or not. Or try with global constants..it should work...
Regards,
Joy.

Problem with .DLL and global variables

Hi,
I need some helps to figure out my problem.
I wrote a .dll file to open and run a GUI. When I run it at the first time, it is ok. When I call it again, there is an error "Pointer to free memory passed to library. It will be ok if I completely exit the program that calls the .dll before re-call it. I think there is some problems with global variables when I call another thread. How can I free global variables between threads. Is there any solution for this problem?
Thanks

Vinh Pham:
Are you doing anything intentionally that frees your globals?
CVI ships with an example program that demonstrates calling a DLL to create a user interface: guidll.cws.
I made two simple modifications to guidll.cws.
1. In guidll.c, I made hpanel global by moving its declaration from RunDLLUI() to right below the #include statements.
2. In useguidll.c, I duplicated the lines calling RunDLLUI () and MessagePopup() to call the DLL gui twice.
I built the project and ran it. I had no problems with free'ed globals.
Take a look at the guidll example.
Can you either post your code or a modification to guidll that demonstrates the problem you're having?

How can I pass a value field to a global variable?

I have a doubt,
I wnat to know if is possible to pass a value field to a global variable inside of DataFlow?
That a try to do is at the time to execute a JOB on line (real time), depending of the value field that i receive, only certain DATAFLOWS will be executed depending of the value field.
I hope you can help me.
Kind regards!!!

It can be done via various ways, your approach is kind of odd, though.
You are saying you have one kind if Input message, depending on the flag you want to do different transformations. The way you envision that is by loading that flag into a global variable and use different dataflows then.
Can you use different dataflows within one Realtime Job? Yes, usually the first loads an in-memory datastore.
Can you write into a global variable? Yes and No. Not directly, but you can write the value into e.g. a database and using the sql() function read it from there. But why would you. You could write it into the in-memory datastore. And then you run your n dataflows, each has a filter. So only one of these dataflows will actually process the data.
Are there other approaches? I would have a Case transform at the beginning and route the data into different queries depending on the data. So all in one dataflow. Your approach is fine for a batch dataflow where a dataflow is started, does something and then ends. But that's not how it works in Realtime!

How do I store VI References in global variables and access them later

From what I know, Labview automatically deletes VI references when they go out of use. Is there a way for me to override this so that I can access a set of preloaded references in a separate VI? Essentially I would like to open the VI's dynamically into the memory, store the references in global variables and access them at a later time. The VI's I'm referencing won't be known until runtime. I know its not the safest way to do it, but it would be the most productive on my end.
Thank you
Clay Upton

I'm not sure what you mean by "a later time", but a VI reference will remain valid as long as the VI is in memory. If you don't unload the VIs, the references will remain valid.
If you do need to unload the VIs, for whatever reason, I would suggest the following:
Create a functional global as your interface for obtaining the references.
Feed the paths to the VIs into the VI when initializing it (since you don't know which VIs in advance).
When calling the VI to obtain the references, have the VI check them first (using the Not a Number... primitive). If it sees that they're invalid, it can open a new reference and return that.
You should note that when a VI is removed from memory, the data space is used is released, so if those VIs are expected to hold data (using shift registers, etc.) this will be a problem.
The description I've given will only be usable in certain instances (and it has its intricacies), but you didn't really give any details about what you're actually trying to accomplish.
Try to take over the world!

Global Variable in Oracle Forms 6i

Hi,
How & where to define global variable in Oracle form 6i and also let me know how to access it.
Thanks in advance
Regards,
Sanket

hi
Global variable are forms specifice variable.
it can store character value upto 255 for all usages.
We can initialize it when we declare otherwise give error if we did not assign it any value.
Oracle 10g it can take upto 4000 bytes
GLOBAL.ur_globalvar := TO_CHAR(15);
or
:GLOBAL.ur_globalvar:= '15';
or
Remmber numeric values are implicitly converted by oracle 2 character
:GLOBAL.ur_globalvar:= 15;
-- which can then subsequently be accessed using...
:GLOBAL.ur_globalvar;
-- To destroy a global variable and release its memory, use the ERASE built-in procedure:
Erase('GLOBAL.my_var'); Regards,
Abdetu...

What are the best practices to use GLOBAL Variables

Hi,
Please guide how Global Variables can be declared and how they can be initialized.
Further please guide what are the impacts of Global Variables(if any) on the memory of CLIENT or SERVER, if they are not initialized or freed up after usage.
Thanks.
Regards.

spilgrim wrote:
My preference is not to use them and to use parameters or package variables. There is not real control on globals so you can end up with an applicatios that has lots of them that are only used once but persist for the user session.I second that. I don't know how often I searched for bugs caused by typos in the names of global variables. Plus the fact that they are only of datatype VARCHAR2. If you are using share_library_data you could also use Package globals in a forms library to share data between called and calling forms. Or you could use a database package...
cheers

Can LabVIEW global variables be shared between UUT sequence steps in the parallel sequence model?

Sorry for this simple question, I'm having a hard time finding this answer.
If I launch a sequence to run on two UUTs in the parallel sequence module, can I get both UUTs to run LabVIEW vis that use global variables such that :
1) UUT 0 executes 20 LabVIEW Vi steps asynchronously, 5 of which access data from LabVIEW global variables A, B, C (Strings)
2) UUT 0 executes the same 20 LabVIEW based steps asynchronously 5 of which access data from then same LabVIEW global variables A, B, C (Strings)
I am a little worried that using file globals may have some delays or more of a race condition than using native LabVIEW global variables like in a single labview application perform.
QUESTION 2: Are file globals actually written to the hard drive and shared between parallel sequences through file transfer? OR are they in memory?
Brad Whaley
LabVIEW Certified Engineer

Hi bdwhaley,
Are your parallel sequences only reading from the global variable? Or are they writing to the variable as well? If it is just reading, then you should be okay. File globals are read from memory. Every time they are read, a copy of the data is made in memory.
Humphrey H.
Applications Engineer
National Instruments

Call function in LabView from a DLL, then access global variable from DLL

I have created a DLL in LabWindows with a function and a structure. I want to call the function from within LabView and then access the global structure. I am able to call the function from the DLL with a "Call Library Function Node" and can access the return value, but I cannot figure out how to access the global structure. The structure is declared in the DLL header file with __declspec(dllimport) struct parameters.
Is there any way of accessing this structure without using the Network Variable Library?
Solved!
Go to Solution.

dblok wrote:
When you say "access to" or "the address of" the global variable, do you mean to pass the variable as an argument to the function call in the DLL? If so, then I was not really sure how to pass a cluster from LabView by using the "Call Library Function Node".
Yes, that's exactly right. I would include a pair of helper functions in the DLL to read and write the global variable. Alternatively you might write separate helper functions for each field inside the global structure, depending on the number of fields and whether you want to do any validation on the values.
You can pass a cluster by reference to a function that expects a struct by setting the parameter to Adapt to Type, so long as the cluster does not contain any variable-length elements (strings or arrays). The cluster needs to match the struct exactly, and sometimes that involves adding extra padding bytes to make the alignment work. Variable-length elements in LabVIEW need to be converted to clusters containing the same number of elements as the struct definition (for example, if your struct contains char name[12], you would create a cluster of 8 U8 values, and you could use String to Array of Bytes followed by Array to Cluster to convert a LabVIEW string into that format). If the struct contains pointers it gets more complicated, and it may be easier to write functions in the DLL to access those specific elements individually.
If you can't get this working or need help, post your code and an explanation of the error or problem you're seeing.
EDIT: it is also possible to include a single function in the DLL that returns the address of the global variable, which LabVIEW can then use to access and modify the data, but that's more complicated and likely to lead to crashes if you don't get the memory addressing exactly right.

JSP Global Variable in MultiUser Environment???

Hi,
I heard that my Boss, taking about the declaration of the Global variable in Jsp will create a problem in the Multi-User Environment.
Is it true?? If so ,What is the actual problem? It occupies more memory when compared to the Local variable??
Isn't it a bad option to declare unless u want it badly??
I am not able to find a suitable link for this..
Pls. do respond for this....
Thanks,
JavaCrazyLover

Its bad because global variabels will be used and changed by different users at same time.
This will lead to variuos problem like user1 setting the variabel, user2 seting it , user1 using it with the value user2 set.

Can I read/write global variables that are in other PC?

I attach the vis and the executables.
My problem is that when I run( continuosly, because in other way, I read the default value of the variable) getvalue.vi and setvalue.vi, I don´t have any problem, I can read/write the global variables, the two vis is running in the same PC.
But when I do the exe and I run them continuosly , it doesn´t work.
Any solution?
Thanks in advanced!
Graci
Attachments:
Get_Value.vi ‏30 KB
Set_Value.vi ‏30 KB
Exe.zip ‏272 KB

Hello Bichillo,
By running the vis continuously you are running into race conditions. If you cannot control when you are writing to or reading from a global variable, you cannot know whether the value writen/read is the right one or not.
In your case the global variable value that is read is sometimes the last value writen and sometimes an empty string.
To make the global variable behave as desired, that is, keeping its last value, the global variable must be in memory when you access it using VI Server. If it is not in memory, the returned value is an empty string. That´s why you sometimes get a non-empty string: when you access the global variable to read its value, it happens to be in memory because you´ve just writen to it.
To ensure that the global
variable is always in memory and it keeps its last value, you must include the global variable into your block diagram. I am attaching modified vis that implement this.
Hope it helps.
César Verdejo
Training and Certification | National Instruments
Attachments:
Get-_Set_Value.llb ‏48 KB

Using a global variable within a function

Hi all,
I'm trying to learn how to use global variables, but can't quite get it right:
Im trying to use two buttons, named UpButton and DownButton to control one global variable, p1
A text field, named "Value" displays p1.
Here's my code:
p1 = 0;
ButtonClick("UpButton", p1, 100,"Value");
ButtonClick("DownButton", p1,(-100),"Value");
function ButtonClick(ButtonName,Var,Increment,TextToChange){
                    sym.$(ButtonName).click(function(){
                    Var = Var + Increment;
                    sym.$(TextToChange).html(Var);
However, it seems to be treating p1 as two different variables.
Here's a link to the page to show you what I mean, apologies but this link wont work in google chrome because I'm using dropbox as a server temporarily
In other browsers you may need to click "Show all content" or similar to any security warnings...
https://dl.dropboxusercontent.com/u/83693404/ButtonTest/buttons.html
Here are the project files:
https://app.box.com/s/0shocivto8fl295h62uq
Any help greatly appreciated, sorry if this is a stupid question,
Katherine

Hi Katherine,
However, it seems to be treating p1 as two different variables.
Indeed, your code created two different variables in two different scopes (I guess it as to do with JavaScript closures, but do not ask me more, I am still a bit foggy about that idiosyncrasy ).
In JavaScript, a primitive parameter – this is the case here with p1, a Number value –, is passed by value. In other words, a copy of the value is made. Your code handles two copies of the value stored in p1.
This contrasts with an object parameter, which is passed by reference (address in memory), without copy. Your code would work if Numbers were passed by reference : the two Var (p1) would then point to the same address.
The intent behind your trial is a global variable.
1) Let us be as simple as possible :
Stage : document.compositionReady event handler
p1 = 0;
buttonClick = function( Increment)
p1 += Increment;
sym.$( "Value").html( p1);
Stage : DownButton.click event handler
buttonClick(-100);
Stage : UpButton.click event handler
buttonClick(100);
Without being preceded by the var keyword the variables are global.
So the Number variable p1 can be accessed inside function buttonClick.
And the Function variable buttonClick as well, is accessible inside click event handlers, everything (function definition +function calls) being inside the same symbol (Stage).
2) Now, suppose this is no longer the case : you want to access a variable from another symbol.
We create a new GraySquare symbol, instantiated both in the DownButton symbol (instance name DownSquare) and in the UpButton symbol (instance name DownSquare).
Stage : document.compositionReady event handler
p1 = 0;
sym.buttonClick = function( Increment)
p1 += Increment;
sym.$( "Value").html( p1);
The sym. prefix is now necessary to make the variable (here a Function, but you would proceed exactly the same with a String, Number or Boolean) accessible in other symbols.
DownButton symbol : DownSquare.click event handler
sym.getComposition().getStage().buttonClick( -100);
UpButton symbol : UpSquare.click event handler
sym.getComposition().getStage().buttonClick( 100);
From these other symbols, the sym.getComposition().getStage(). prefix is necessary to acces to our global variable (function).
The two examples are downloadable here : https://app.box.com/s/6vkyiqk7i8zwlw0j1wk1
Gil

Global variables in Oracle 8.1.6 on NT

I am running Oracle 8.1.6 on Windows NT.
Does anybody know how can I create and maintain global variables or even constants, so that the same variables and constants could be used by all connections to the database.
The main feature is that I can store their values in database table or external file, but have not to read these values from table or file every time I need them.
All readings from the source file or table must occur only one time, for example, during database server startup, after it all the values must be supplied directly from phisical memory rather than from the table or external file (to speed up this process).
Thank you.

Your answer lies in one of the new features introduced in the Oracle8i: New Features for Administrators course. You can create a function that executes as soon as the user logs in, loading the variables that are required.

Global variable, memory

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