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Configuration topics for Oracle database on IBM AIX with ONTAP.

Concurrent I/O

Achieving optimum performance on IBM AIX requires the use of concurrent I/O. Without concurrent I/O, performance limitations are likely because AIX performs serialized, atomic I/O, which incurs significant overhead.

Originally, NetApp recommended using the cio mount option to force the use of concurrent I/O on the file system, but this process had drawbacks and is no longer required. Since the introduction of AIX 5.2 and Oracle 10gR1, Oracle on AIX can open individual files for concurrent IO, as opposed to forcing concurrent I/O on the entire file system.

The best method for enabling concurrent I/O is to set the init.ora parameter filesystemio_options to setall. Doing so allows Oracle to open specific files for use with concurrent I/O.

Using cio as a mount option forces the use of concurrent I/O, which can have negative consequences. For example, forcing concurrent I/O disables readahead on file systems, which can damage performance for I/O occurring outside the Oracle database software, such as copying files and performing tape backups. Furthermore, products such as Oracle GoldenGate and SAP BR*Tools are not compatible with using the cio mount option with certain versions of Oracle.

Tip

NetApp recommends the following:

  • Do not use the cio mount option at the file system level. Rather, enable concurrent I/O through the use of filesystemio_options=setall.

  • Only use the cio mount option should if it is not possible to set filesystemio_options=setall.

AIX NFS mount options

The following table lists the AIX NFS mount options for Oracle single instance databases.

File type Mount options

ADR Home

rw,bg,hard,[vers=3,vers=4.1],proto=tcp,
timeo=600,rsize=262144,wsize=262144

Controlfiles
Datafiles
Redo logs

rw,bg,hard,[vers=3,vers=4.1],proto=tcp,
timeo=600,rsize=262144,wsize=262144

ORACLE_HOME

rw,bg,hard,[vers=3,vers=4.1],proto=tcp,
timeo=600,rsize=262144,wsize=262144,
intr

The following table lists the AIX NFS mount options for RAC.

File type Mount options

ADR Home

rw,bg,hard,[vers=3,vers=4.1],proto=tcp,
timeo=600,rsize=262144,wsize=262144

Controlfiles
Datafiles
Redo logs

rw,bg,hard,[vers=3,vers=4.1],proto=tcp,
timeo=600,rsize=262144,wsize=262144,
nointr,noac

CRS/Voting

rw,bg,hard,[vers=3,vers=4.1],proto=tcp,
timeo=600,rsize=262144,wsize=262144,
nointr,noac

Dedicated ORACLE_HOME

rw,bg,hard,[vers=3,vers=4.1],proto=tcp,
timeo=600,rsize=262144,wsize=262144

Shared ORACLE_HOME

rw,bg,hard,[vers=3,vers=4.1],proto=tcp,
timeo=600,rsize=262144,wsize=262144,
nointr

The primary difference between single-instance and RAC mount options is the addition of noac to the mount options. This addition has the effect of disabling the host OS caching that enables all instances in the RAC cluster to have a consistent view of the state of the data.

Although using the cio mount option and the init.ora parameter filesystemio_options=setall has the same effect of disabling host caching, it is still necessary to use noac. noac is required for shared ORACLE_HOME deployments to facilitate the consistency of files such as Oracle password files and spfile parameter files. If each instance in a RAC cluster has a dedicated ORACLE_HOME, then this parameter is not required.

AIX jfs/jfs2 Mount Options

The following table lists the AIX jfs/jfs2 mount options.

File type Mount options

ADR Home

Defaults

Controlfiles
Datafiles
Redo logs

Defaults

ORACLE_HOME

Defaults

Before using AIX hdisk devices in any environment, including databases, check the parameter queue_depth. This parameter is not the HBA queue depth; rather it relates to the SCSI queue depth of the individual hdisk device. Depending on how the LUNs are configured, the value for `queue_depth might be too low for good performance. Testing has shown the optimum value to be 64.