Magento 2 Error Allowed Memory Exhausted Fix complete guide and clarification regarding the cause of the error, solution.
It is due to “allowed memory size of bytes exhausted”.The main purpose of this error is regarding the storage of memory.
If you use more RAM than what you specified in the file called PHP ini then this error gets occur.
Complete guide Magento 2 Error Allowed Memory Exhausted Fix
Using three different methods you can fix this error.

During Magento 2 Installation this error also occurs.
Method 1:
Find the below value and made the change as given to fix the error of memory in the file php.in
.
max_execution_time=18000
max_input_time=1800
memory_limit=4G
After making changes restart the Apache.
Method 2 :
You can also fix this error using the command line for memory limit and this can be done by adding an inside the command
The memory limit for the compilation command.
php -dmemory_limit=4G bin/magento setup:di:compile
The memory limit for deployment command
php -dmemory_limit=4G bin/magento setup:static-content:deploy
To fix the error you add the memory limit change 4G to the max.
Method 3 :
You can also fix by using the command instead of only bin/magento
like given below
php -dmemory_limit=-1 bin/magento ....
Below is an example of the memory limit.
php -dmemory_limit=-1 bin/magento setup:upgrade
php -dmemory_limit=-1 bin/magento setup:di:compile
This error is complete regarding the memory limit which is to be done by configuration in PHP.
A parameter named, -dmemory_limit=-1
via command line helps to run PHP without memory limit.
Conclusion
With the help of the above method, the memory limit errors get fixed.