It depends, depends on what kind of backup mode that you had taken. If you took a full backup by the following ways, then you have a consistent full backup:
User-Managed Offline Backups:
You have to copy all data files and archive logs after a clean shutdown. This is also called cold full backup.
User-Managed Online Backups:
BEGIN BACKUP mode:
You can copy all online data files and archive logs only if the database is in begin backup mode.
SQL> alter database begin backup;
In this mode, you have to ensure that you have enough space to sustain the online redo logs to grow during backup. Additionally, the performance will be getting worse along with the growing online redo logs.
SQL> alter database end backup;
You should be better to archive all online redo logs.
SQL> alter system archive log current;
Open with READ ONLY:Read-only mode is not an actual "online" backup, I would call it as semi-online. Because we cannot do anything except queries. In this way, you have to open the database to read only first, then copy all required data files and archived logs to your backup destination.
I would say that this practice is a compromised backup strategy when you can't do BEGIN BACKUP mode for some reasons. Because users wouldn't understand why the database cannot be read/write. Possibly, they don't even try to understand.
RMAN with MOUNT or READ ONLY:
Backing up full database by RMAN in mount or read only state after a clean shutdown.
Full backups that are other than the above backup strategies are inconsistent. That is to say, duplicating an auxiliary database only by the source of a hot full backup set is not enough, you also need some archived logs to meet the minimal requirement of open resetlogs.
This post is supplementary and extended of my another post relating to how to make a self-contained backup set.