Activating a Physical Standby Database & it's Scenarios

ORA-15018: disk group cannot be created ORA-15099: disk '/dev/disks/ganesh_1' is larger than maximum size of 2097152 MBs.

SQL> CREATE DISKGROUP DG_DATA EXTERNAL REDUNDANCY disk '/dev/disks/ganesh_1';
CREATE DISKGROUP DG_DATA EXTERNAL REDUNDANCY disk '/dev/disks/ganesh_1';
*
ERROR at line 1:
ORA-15018: diskgroup cannot be created
ORA-15099: disk '/dev/disks/ganesh1' is larger than maximum size of 2097152 MBs

The error you're encountering with ORA-15018 and ORA-15099 occurs when attempting to create an Oracle ASM disk group or adding disk in existing diskgroup. 
And the ORA-15099, Indicates that the disk size exceeds the maximum supported size for a particular ASM disk group configuration.

Root Cause:-

The disk '/dev/disks/ganesh1' is larger than 2 TB, but the maximum size that can be supported by your ASM disk group (based on its current configuration) is capped at 2097152 MB, which is around 2 TB. 

You can increase the maximum supported disk size by increasing the AU size (for example, to 4 MB or 16 MB) during disk group creation. As per recommended you can change the AU size, else leave it, follow the below step and troubleshoot. 

TROUBLESHOOT :-

• You must first verify your 'asm_diskstring' argument and provide the correct disk location.
• Verify the new disk's permissions and make the necessary corrections.
• Verify the disk owner, group the new disk, and make the necessary corrections.
• Using below command you can set ASM_DISKSTRING parameter.

SQL> alter system set asm_diskstring='<DISK_LOCATION_PATH_1>', '<DISK_LOCATION_PATH_2>'scope=spfile;

     e.g.

SQL> alter system set asm_diskstring='/dev/disk/ganesh_*' scope=spfile;

• Second, make sure the new disk's header_status is CANDIDATE or FORMER.

set lines 200 pages 200
col path for a70
col name for a40
select name,path,header_status from v$asm_disk where header_status='CANDIDATE' order by path;

• The third step is to verify that the database and ASM are compatible. We were unable to construct the disk if there was any kind of mismatch, which is the measure that caused the aforementioned ORA error.

SQL> select name diskgroup, compatibilty asm_compat, database_compatibility db_compat from v$asm_diskgroup;

DISKGROUP    COMPATIBILITY        DB_COMPATIBILITY 

------------ -----------------   --------------------

OCR_DISK                  19.0.0.0.0              12.2.0.0.0

• Therefore, we mentioned both the compatible.rdbms and compatible.asm properties when we were constructing the new diskgroup. to stay clear of the problem.

create diskgroup (diskgroup_name)  EXTERNAL REDUNDANCY disk '/dev/disk/ganesh_1' 'compatible.rdbms'=12.2.0.0.0', 'compatible.asm'='19.0.0.0.0';

     e.g.

SQL> create diskgroup DG_GANESH  EXTERNAL REDUNDANCY disk '/dev/disk/ganesh_1' 'compatible.rdbms'=12.2.0.1.0', 'compatible.asm'='19.0.0.0.0';

      O/P : - 

select group_number, name, compatibility, database_compatibility from v$asm_diskgroup;
GROUP_NUMBER   NAME    COMPATIBIL  DATABASE_C
------------     --------------------   ----------      ----------
           1 OCR_DISK       19.0.0.0.0    12.2.0.0.0
           2 DG_GANESH     19.0.0.0.0  12.2.0.0.0

Note :- 

During addition of time if you are facing same ORA error then you can resize the disk using below command.

SQL> alter diskgroup <DISKGROUP_NAME> resize all;

Additional :-

We have used the command below to create a new diskgroup. We didn't receive any errors at that time because the compatible.rdbms and compatible.asm attributes were identical.

create diskgroup (diskgroup_name)  EXTERNAL REDUNDANCY  disk '/dev/disk/ganesh_1';

e.g.

SQL> create diskgroup DG_GANESH  EXTERNAL REDUNDANCY  disk '/dev/disk/ganesh_1';

SQL> select name diskgroup, compatibilty asm_compat, database_compatibility db_compat from v$asm_diskgroup;
DISKGROUP    COMPATIBILITY        DB_COMPATIBILITY 
------------              -----------------           --------------------
OCR_DISK          19.0.0.0.0          19.0.0.0.0
 DG_GANESH     19.0.0.0.0         19.0.0.0.0

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