We have a standby server but it is logically mirrored. We cannot see the files in the standby server. Do you have any suggestions?
Unless you have implemented a clustered file system, the two servers on the SAN won't be able to see the other server's files.
Depending on the maintenance you need to perform, Data Guard may not help you achieve zero downtime for the maintenance. You might point out to the client that maintenance is necessary at some point -- otherwise the database will not perform as expected. That being said, there are fewer and fewer maintenance operations that need to be performed offline any more. Many maintenance commands now include an ONLINE parameter to perform the command while the database is up and running. I'm not sure what maintenance operations you are trying to perform, so I cannot be more specific.