Make Room for the Update
The Android Pie update is a pretty big download and some of you will need to make room for it.
If you're coming from the Android Pie beta, your update will probably be a few hundred megabytes. However, if you're coming from Android Oreo, your Galaxy A's Android Pie update will likely be in the neighborhood of 1.7GB.
If you have a ton of space on your internal storage, installing it won't be a problem. If you're running out of storage, you will have to delete files to make room.
If you're nearing the threshold (or even if you're not) use this time to do some early spring cleaning.
If you've had your device for awhile, you've probably accumulated a lot of clutter you can get rid of. Dig into your files (photos, videos, etc) and delete the files you no longer need.
If you don't know where to start, you can use the Device maintenance feature located in your Settings to help narrow down the files to delete from your phone.