Identify files in ASM not known to DB

Question

I have inherited DBA responsibilities for an old Production system that has two physical stand-by systems. All three DBs use ASM (10.1.0.4) and each each ASM supports only one DB. While gathering space usage numbers to estimate when the underlying SAN storage systems would be maxed out, I discovered that one physical stand-by DB (aka Standby D) showed ASM using more storage space than either the other stand-by database or production.
In short, there are more files on the Standby D ASM than the other stand-by ASM.
If I go into the database and query v$datafile_header (the DB is applying archive logs so I did not stop the managed recovery process just to open the DB for dba_data_files access) I see entries such as
+GROUP15K/scrtvprd/datafile/outln.341.727897397
+GROUP15K/scrtvprd/datafile/system.330.727882901
When I look in ASM as shown by this standard query
select concat('+'||gname, sys_connect_by_path(aname, '/')) full_alias_path,
       system_created, alias_directory, file_type
from ( select b.name gname, a.parent_index pindex, a.name aname,
              a.reference_index rindex , a.system_created, a.alias_directory,
              c.type file_type
       from v$asm_alias a, v$asm_diskgroup b, v$asm_file c
       where a.group_number = b.group_number
             and a.group_number = c.group_number(+)
             and a.file_number = c.file_number(+)
             and a.file_incarnation = c.incarnation(+)
where alias_directory = 'N'
start with (mod(pindex, power(2, 24))) = 0
            and rindex in
                ( select a.reference_index
                  from v$asm_alias a, v$asm_diskgroup b
                  where a.group_number = b.group_number
                        and (mod(a.parent_index, power(2, 24))) = 0
                        and a.name = '&DATABASENAME'
connect by prior rindex = pindex;It shows full_alias_paths as
=+GROUP15K/scrtvprd/DATAFILE/OUTLN.285.727841595 -- not shown above
=+GROUP15K/scrtvprd/DATAFILE/outln.341.727897397
=+GROUP15K/scrtvprd/DATAFILE/SYSTEM.318.727827977 -- not shown above
=+GROUP15K/scrtvprd/DATAFILE/system.330.727882901
ASM shows 112 files in the system, but the DB only shows 70 via the above two methods.
My thought is the RMAN rebuild of the Standby D system several years ago failed and the previous DBA missed all the data file clean-up following that failure.
Question:
Besides using my eyeballs to match up the names to see what is in use and not, is there another way to get Oracle to tell me this? It seems the control file is the only object that translates between what the ASM v$asm views show and the database v$ views show, but I wanted a second opinion to see what others know.
My goal is to delete the extra ASM files that the DB does not know about to free up 500+ GB of disk space.

Answer 1

My recommendation is that you create a set of files showing what you see and upload them to MyOracleSupport as part of an SR.
Critically important to understanding what you can and can not touch is knowing last accessed/changed dates. Dynamic performance views such as:
gv$asm_disk
gv$asm_disk_stat
gv$asm_file
desc gv$asm_filesystem
Should be part of your analysis.
Keep in mind there may be other databases, even old ones that have been shut down, that have ASM storage.