Wednesday, August 8, 2018

Is it possible to use '-' sign (dash/hyphen/minus) in the hostname of Exadata ?

 The problem started from error:

CellCLI> list cell
     ed04celadm01     online

CellCLI> alter cell name = ed04-celadm01;
                                ^
CELL-01504: Invalid command syntax.

CellCLI> alter cell name = 'ed04-celadm01';

CELL-00012: Name value is not valid. ASCII characters a-zA-Z_0-9 required.

CellCLI> alter cell name="dc1-exa1celadm01";

CELL-00012: Name value is not valid. ASCII characters a-zA-Z_0-9 required.


So, the query is: is this possible to use '-' (dash/hyphen/minus) in the Exadata hostname or not ?

As shown above, Oracle prohibit to use dash in the name.

But, in other side, one our customer (large bank) has corporate standard, which require prefix in hostname: LOCATION-EXADATA#-HOSTNAME, for example: dc1-exa1-celadm01  (dc is datacenter name). And they used its corporate standard for many years and have no problems with hostname. And they bought the Exadata. And we need to run this machine.

The documentation say nothing about allowed characters in Exadata hostnames.

We checked: OEDA allowed the '-' sign in the prefix.
So me decided to install Exadata with dash in the hostname.
And installation was successful !

What the matter, what is the difference ?
 
The investigation shows that all hostnames have '-' in the name:
10.18.82.11 dc1-exa1-dbadm01 dc1-exa1-dbadm01.corp.icba.biz
10.18.82.12 dc1-exa1-dbadm02 dc1-exa1-dbadm02.corp.icba.biz
10.18.82.13 dc1-exa1-celadm01 dc1-exa1-celadm01.corp.icba.biz
10.18.82.14 dc1-exa1-celadm02 dc1-exa1-celadm02.corp.icba.biz
10.18.82.15 dc1-exa1-celadm03 dc1-exa1-celadm03.corp.icba.biz
10.18.82.21 dc1-exa1-sw-adm01 dc1-exa1-sw-adm01.corp.icba.biz
10.18.82.22 dc1-exa1-sw-iba01 dc1-exa1-sw-iba01.corp.icba.biz
10.18.82.23 dc1-exa1-sw-ibb01 dc1-exa1-sw-ibb01.corp.icba.biz
10.18.82.24 dc1-exa1-sw-pdua01 dc1-exa1-sw-pdua01.corp.icba.biz
10.18.82.25 dc1-exa1-sw-pdub01 dc1-exa1-sw-pdub01.corp.icba.biz


But CELL NAME was different !

CellCLI> list cell
       dc1_exa1_celadm01  online


Look: Oracle internally put the _ instead of -

And all celldisk and griddisk names are of the same style:


CellCLI> LIST CELLDISK
       CD_00_dc1_exa1_celadm01  normal
       CD_01_dc1_exa1_celadm01  normal
...
       FD_00_dc1_exa1_celadm01  normal
       FD_01_dc1_exa1_celadm01  normal
       FD_02_dc1_exa1_celadm01  normal
       FD_03_dc1_exa1_celadm01  normal

CellCLI> LIST GRIDDISK
       DATAC1_CD_00_dc1_exa1_celadm01  active
       DATAC1_CD_01_dc1_exa1_celadm01  active
...
       RECOC1_CD_00_dc1_exa1_celadm01  active
       RECOC1_CD_01_dc1_exa1_celadm01  active

...


Conclusions:
- It is safe to use '-' in the hostname of the Exadata.
- Divide the HOST name and CELL name (name in cellcli)
- The sign '-' take 1 place. As you should know the Grid Disk Name is limited by 23 chars. Additional chars lead to overallocation (exceeding this limit). So, i recommend - avoid '-' in the host names.


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