Reducing file size/how does purge work?

[MisterJingles]

Hi guys

 

I have 2 questions.

 

1) What is the most effective way to reduce the size of my drawing? Does freezing layers or turning layers off do this?

 

2) I know PURGE is a way to remove unecessary layers but I want to know how does Autocad know these layers are not needed and can be deleted?

 

Thanks

Rob

[phobos]

Hi Rob,

Maybe these can helpful

 

Answer 1: using less viewports and layout tabs as less as possible

Answer 2: only if these layers are empty

[AlinOz]

I think Phobos got a little lost on what you were chasing...

 

1. The most effective way of reducing your drawing size is by purging unused objects. If you're working with Dynamic Blocks and Hatches, AutoCAD will produce Unnamed Blocks (*Uxx) by the dozens (each time you alter a Block or Hatch, it will produce an unnamed Block). Purge will get rid of them and produce a smaller file.

Other than that, there is very little can be done other than to write parts of a drawing out as a new file to XREF back in. This will reduce your file size, but won't make it work faster because once the xref is imported, it will still have the same objects loaded (unless you clip it wherein it 'forgets' those clipped out objects).

Freezing and Turning Off layers won't reduce the size of the file, but it can assist with speeding the system up. Firstly let's define how AutoCAD works- it has 2 databases - The Drawing Database and a Display List (which is what you see on the screen). Purging will decrease the size of the Drawing Database. Freezing has the potential to decrease the size of the Display List - Freezing Layers flags objects on a layer and tells AutoCAD to ignore them when it regenerates and don't put them into the Display List. Thus a smaller Display List Database is produced leaving more memory for other operations and less objects for it to deal with. Turning Layers Off still write the Objects into the Display List, but they're flagged not to show. This doesn't provide any speed boost other than the fact that when the layers are turned on a regen isn't required to display them.

 

2. When you Purge, AutoCAD will scan the Database to see if there are any objects that have a reference to the Layer (each object has attributes such as Layer, Colour, Linetype, PlotStyle, etc... and others dependent on their object type). If there's no reference, it will advise you and allow you to choose whether you want to ditch it or not...

 

OK, that was a biggie, but I hope it explains it well enough for you to make some educated decisions...

[MisterJingles]

Yeah that helps me alot. Thanks a stack Alin.

 

Thanks phobos.

[aLiCaD]

1) What is the most effective way to reduce the size of my drawing? Does freezing layers or turning layers off do this..

 

Answer

 

a. check your drawing layer, removed or delete un useful layers.

 

2) I know PURGE is a way to remove unecessary layers but I want to know how does Autocad know these layers are not needed and can be deleted?

 

Anwser

 

As what I experience, cad can detect itself of what layers is always unused. Maybe these layers are those duplicated or semi-same layers.

[MisterJingles]

Ok I made a duplication of my drawing and purged one copy but now its not smaller but in fact very slightly bigger. From 10.9MB to 11MB.

How is that?

[Ryder76]

Ok I made a duplication of my drawing and purged one copy but now its not smaller but in fact very slightly bigger. From 10.9MB to 11MB.

How is that?

 

That's weird - what file format do you save your drawing to?

 

Before I came to this company the drafters were using 2006 & 2009 and saving all of their dwg's to 2000. HOLY COW! The reason they were doing that was someone in the shop only had ACAD 2000 and they saved them so he could access them. First he didn't need to be able to access them he really only needed to view them. The other reason was for clients to be able to use them. Well, we decided to start saving them to 2007 as a rule and if there was a client need we would save down to their version to send to them. The file sizes were cut in half.

 

Hope this helps.

[MisterJingles]

No Im running 2007 LT and saving it as a normal .dwg file. Nothing fancy.

 

Ok please dont think Im on drugs but the purged one is now smaller, but only a little.

 

Purged 10.7 MB (11,322,532 bytes)

Unpurged 11.0 MB (11,580,017 bytes)

 

Is this the difference I shouldve expected?

[GCarr78]

No Im running 2007 LT and saving it as a normal .dwg file. Nothing fancy.

 

Ok please dont think Im on drugs but the purged one is now smaller, but only a little.

 

Purged 10.7 MB (11,322,532 bytes)

Unpurged 11.0 MB (11,580,017 bytes)

 

Is this the difference I shouldve expected?

Well, it can vary from file to file.

 

If there your file is as efficient as it can get then yes, you are probably as small as you can go.

 

Try this also (note this wont work if using model and paper space or files with xrefs) show the file as you want it displayed, proper layers and objects showing. Create a block file wblock of the entire drawing. I find that works to get rid of stuff the purge command doesn't!

 

If you have xrefs in your file, purge them also. Large blocks may also contribute to your file size create xrefs of those instead of blocks. I don't know what you are drawing so I can't speak to what the file size SHOULD be under normal conditions but 10MB does seem big.

[MisterJingles]

Thanks GCarr. Its quite an elaborate drawing of an entire beachfront promenade. So perhaps 10mb is accceptable?

[Jack_O'neill]

Keep in mind too guys, that "purge" won't always get everything on the first pass. If you have unique layers and linetypes and stuff in nested blocks (a block in a block in a block), it may take running purge 4 or 5 times to get it all. I created a button that does a "purge all" 6 times just to be sure.

 

File size can really be affected by drawing style and methods too. You probably know this already, but if you have a drawing that uses the same window for example in several places, making that window into a block and then copying the block to each location will result in a smaller file as opposed to copying the individual lines. That will only work with regard to file size if you use the exact same block over and over again (and don't explode them). If you have 10 windows, and they are all different, making 10 different blocks will actually increase the file size. The rub here is that if your drawing is likely to change, having stuff like doors and windows and such as blocks can really make it easier to reposition stuff. The increase in file size might be worth it if it makes doing your revisions easier and quicker.

 

Oh, and one other thing. You mentioned that purging made the copy slightly larger. It will show up as bigger until you save and close the drawing. It's holding the "undo" information up to that point.

[pattyandme]

You could also change the drawing from 3d to 2d for certian features for example I use lattice work in my drawings trying to make them 3d is very memory consuming so i draw it in 2d create a surface and then color it with a texture.

sence the view is only 1 surface it seems to work out.

[GCarr78]

Perhaps, but I'll leave that at your discression.

[GCarr78]

That last comment was for MisterJingles...

 

But Jack does make some good points, hense I find that "wblock" of a file works very well, sometimes in combination with purge.

 

And yes "flatten" would aslo help in some instances..all good methods

[MisterJingles]

Ok thanks guys. That makes sense.

I find myself using blocks pretty often and keep them universal as far as possible. In my line of work Im doing additions to existing drawings so I guess the size is pretty much determined by the person doing the original drawing as the bulk is done there. My additions are small in comparison most of the time.

 

Many thanks