The Impact of "ORA-04068" Error
To gauge the impact of ORA-04068, all you have to do is google it. Two of the main impacts are as follows.
1. Most enterprise applications use connection pool in which connections are cached. Now whenever a new package definition has to be deployed, it needs to be recompiled in production. The moment you do that, for all the connections in the connection pool, the state of this package would be invalidated since the package was re-compiled after the connection was obtained (as part of the connection pool initialization sometime earlier.) Note that this is true regardless of whether you changed the state or not, whether you even changed the code or not. The very first time a procedure or function in this package is invoked, it would fail with the "ORA-04058" error. So typically, you have to remember to "flush" the connection pool (meaning discard existing connections and obtain new connections to Oracle.) This typically leads to a downtime in the application deployment. For example, if you are using tomcat and a connection pool within tomcat, you may have to bring down tomcat and bring it back up - so that it re-initializes the connection pool. What if a long-running batch is using one of the connections to execute some logic completely independent of the package that needs to be recompiled? You would either have to wait till the batch completes or kill it during deployment so you can re-initialize the connection pool. As you can imagine, this can be a nightmare in terms of availability of the application.