# Mmap access denied with SharedArrays

**URL:** <https://discourse.julialang.org/t/mmap-access-denied-with-sharedarrays/44881>\
**Category:** Performance\
**Tags:** parallel, distributed, mmap\
**Created:** [August 13, 2020, 3:34pm UTC](https://discourse.julialang.org/t/mmap-access-denied-with-sharedarrays/44881 "2020-08-13T15:34:26Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![mfariacastro](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mfariacastro/32/4432_2.png) [@mfariacastro](https://discourse.julialang.org/u/mfariacastro)\
**Post date:** [August 13, 2020, 3:34pm UTC](https://discourse.julialang.org/t/mmap-access-denied-with-sharedarrays/44881/1 "2020-08-13T15:34:27Z")

</div>

I am running 1.5.0 on Windows. I keep running into an issue when creating a SharedArray. I am able to replicate the problem about 30% of the time. This is very annoying as it essentially means my code keeps crashing. This is the error message:

```julia
ERROR: LoadError: SystemError: mmap: Access is denied.
Stacktrace:
 [1] windowserror(::Symbol, ::UInt32; extrainfo::Nothing) at .\error.jl:183
 [2] #windowserror#50 at .\error.jl:182 [inlined]
 [3] windowserror at .\error.jl:182 [inlined]
 [4] mmap(::Mmap.Anonymous, ::Type{Array{Float64,3}}, ::Tuple{Int64,Int64,Int64}, ::Int64; grow::Bool, shared::Bool) at D:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.5\Mmap\src\Mmap.jl:224
 [5] mmap(::Mmap.Anonymous, ::Type{Array{Float64,3}}, ::Tuple{Int64,Int64,Int64}, ::Int64) at D:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.5\Mmap\src\Mmap.jl:189
 [6] _shm_mmap_array(::Type{T} where T, ::Tuple{Int64,Int64,Int64}, ::String, ::UInt16) at D:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.5\SharedArrays\src\SharedArrays.jl:670
 [7] shm_mmap_array(::Type{T} where T, ::Tuple{Int64,Int64,Int64}, ::String, ::UInt16) at D:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.5\SharedArrays\src\SharedArrays.jl:649
 [8] SharedArray{Float64,3}(::Tuple{Int64,Int64,Int64}; init::Bool, pids::Array{Int64,1}) at D:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.5\SharedArrays\src\SharedArrays.jl:118
 [9] SharedArray at D:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.5\SharedArrays\src\SharedArrays.jl:105 [inlined]
 [10] #_#10 at D:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.5\SharedArrays\src\SharedArrays.jl:161 [inlined]
 [11] SharedArray at D:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.5\SharedArrays\src\SharedArrays.jl:161 [inlined]
 [12] #_#15 at D:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.5\SharedArrays\src\SharedArrays.jl:171 [inlined]
 [13] SharedArray at D:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.5\SharedArrays\src\SharedArrays.jl:171 [inlined]

```