RAID1 – Zwei spiegelnde Platten

RAID1 Spiegelplatten

SQL*Plus connect strings/logon strings have a couple of special characters, notably these two:

• / (slash) to separate username and password
• @ (at) to separate the TNS descriptor string

If you need to use those characters literally in the logon string, you need to tag them with literal double quotes (literal means: the quotes need to be passed to SQL*Plus, I’m not talking about the UNIX shell):

• Less readable:

  $ sqlplus USER/\"PASS/WORD\"

• More readable:

  $ sqlplus USER/'"PASS/WORD"'

For some systems a downtime is complicated to organize, or bad at all. We have such a system, a RAC database.

In the past, all storage migration operations there had two problems that lead to downtime:

• CRS votedisk migration at best only with offline CRS
• kick old devices from the device management in the operating system

In December I migrated the system to something more modern

• SLES11
• Oracle Grid Infrastructure (CRS/ASM) 11.2
• Oracle Database 10.2.0.5 (yes, still quite old, but it has to be a 10.2 for now)

The use of a modern Linux kernel (especially a modern SCSI stack) and 11gR2 infrastructure fixed all my trouble from the past.

Votedisk

With 11gR2 Grid Infrastructure, the clusterware manages its vital files (VD, OCR) using an ASM instance. A migration of the ASM diskgroups holding these files is now as easy as a migration of a normal diskgroup. ASM takes care of moving the votedisks and the OCR and collaborates with CRS here.

Linux devices

The new Linux kernels with a finally sane SCSI stack and native multipathing helps with the second problem. It’s not a problem anymore to remove old device references from the stack:

• deconfigure the devices from multipathd (not needed technically, since multipathd itself holds no device references)
• remove the device references from the Linux device mapper

  # see /dev/mapper/* for the name
  dmsetup remove mpathX

• remove the LUNs from the SCSI stack

  # X:X:X:X LUN number
  echo 1 > /sys/bus/scsi/X:X:X:X/delete

After that, you can safely edit the FC zone – no errors should occur in any logs.