Fixed :Oracle Database 12c EE -ORA-48122: error with opening the ADR block file

[chiroito]

Docker host using file system such as NFS and ZFS which does not support O_DIRECT can run database container without ADR error adding -v [volume:]/opt/oracle/diag. #241

[brunoborges]

This is such a minor change for a specific case that I wouldn't even bother taking in. @gvenzl, what do you say?

[gvenzl]

I somewhat agree. Trying to find out what Docker says in general for storage that doesn't provide O_DIRECT. I think that even this change wouldn't be enough. Whenever there is something written in the container that uses O_DIRECT this would be a problem. Exposing all possible locations via VOLUME doesn't make much sense.
I also don't understand why you would expose the diag directory via VOLUME to put it then onto a mount that does support O_DIRECT. Why would you not just put the entire container onto that mount in the first place?

[brunoborges]

@gvenzl should we close this one then, since there's agreement?

[gvenzl]

Let's just double check what or whether @Djelibeybi has an opinion about whether you should or shouldn't run a container on a file system that doesn't support O_DIRECT.

[Djelibeybi]

We don't support ZFS on Oracle Linux at all, so that's a non-starter. I'm surprised it doesn't work with NFS, though.

Either way, I feel this should just be documented so that users can make their own modifications if necessary.

[gvenzl]

Where would be the best place to document this? This will affect any Oracle Linux based container that uses O_DIRECT, not only the database one.

[Djelibeybi]

@gvenzl any container that requires O_DIRECT should document it. In this case, document it for the Database container. Oracle Linux itself has no requirement for O_DIRECT. It's purely an application-level requirement.

[brunoborges]

@Djelibeybi but you think this should be defined at the Dockerfile for DB? Or something that people should customize if they really need/want to?

[Djelibeybi]

@brunoborges it should be documented in the README so that customers can customise if they want to. I don't think we need to modify the Dockerfile itself.

[brunoborges]

Got it. @gvenzl can you please close this PR as soon you add the description in the README?