IPhone : JSON Store password maximum length - IBM MobileFirst Platform Foundation 6.3

I have created an App in IBM MobileFirst Platform Foundation 6.3 targetting Android and iPhone devices [Windows Phone in future]. App uses JSON Store Feature.

Following are the procedures.

1. Ask for password from the user.
2. Once user entered the password, encrypt it with the help of SHA256.[When I am converting the password string to a encrypted format [SHA256], i am getting 64 characters.]
3. Now use the encrypted password for protecting the JSON Store.

When I tested this scenario in Android and iPhone devices, it's working perfect.

Now my question is,

1. I am using 64 characters as JSON Store password, will it affect the performance of the app in any case.
2. What is the maximum length of JSON Store password.