Cannot find mean file while training on Imagenet - caffe

Question

I am trying to train and validate a network on Imagenet. The validation process works without any problems (with the pretrained weights). However, when I try to perform the training, there appears an error that the imagenet_mean.binaryproto file is not found; the very same file that has worked for the valiudation process. What is wrong?
...
I0222 15:29:15.108032 15823 net.cpp:399] data -> label
I0222 15:29:15.108057 15823 data_transformer.cpp:25] Loading mean file from: /home/myuser/learning/caffe/data/ilsvrc12/imagenet_mean.binaryproto
F0222 15:29:15.108577 15830 db_lmdb.hpp:14] Check failed: mdb_status == 0 (2 vs. 0) No such file or directory
*** Check failure stack trace: ***
# 0x7fc82857edaa (unknown)
# 0x7fc82857ece4 (unknown)
# 0x7fc82857e6e6 (unknown)
# 0x7fc828581687 (unknown)
# 0x7fc828ba115e caffe::db::LMDB::Open()
# 0x7fc828b75644 caffe::DataReader::Body::InternalThreadEntry()
# 0x7fc828cc1470 caffe::InternalThread::entry()
# 0x7fc81f4a8a4a (unknown)
# 0x7fc826a98184 start_thread
# 0x7fc8271b437d (unknown)
# (nil) (unknown)
Aborted (core dumped)
Here is the prototxt I am using:
name: "CaffeNet"
layer {
name: "data"
type: "Data"
top: "data"
top: "label"
include {
phase: TRAIN
}
transform_param {
mirror: true
crop_size: 227
mean_file: "/home/myuser/learning/caffe/data/ilsvrc12/imagenet_mean.binaryproto"
#mean_file: "data/ilsvrc12/imagenet_mean.binaryproto"
}
# mean pixel / channel-wise mean instead of mean image
# transform_param {
# crop_size: 227
# mean_value: 104
# mean_value: 117
# mean_value: 123
# mirror: true
# }
data_param {
source: "examples/imagenet/ilsvrc12_train_lmdb"
batch_size: 256
backend: LMDB
}
}
layer {
name: "data"
type: "Data"
top: "data"
top: "label"
include {
phase: TEST
}
transform_param {
mirror: false
crop_size: 227
mean_file: "/home/myuser/learning/caffe/data/ilsvrc12/imagenet_mean.binaryproto"
#mean_file: "data/ilsvrc12/imagenet_mean.binaryproto"
}
# mean pixel / channel-wise mean instead of mean image
# transform_param {
# crop_size: 227
# mean_value: 104
# mean_value: 117
# mean_value: 123
# mirror: false
# }
data_param {
source: "/sdc/repository/myuser/Imagenet2012/Imagenet2012trainLMDB"
#source: "examples/imagenet/ilsvrc12_val_lmdb"
batch_size: 50
backend: LMDB
}
}
layer {
name: "conv1"
…