Showing posts from January, 2014

configure DNS for Installtion of Oracle Grid Infrastructure RAC cluster

1.create these files :-, and named.rfc1912.zones into /var/named/chroot/var/named
2.content of :- $TTL 86400 @          IN     SOA    rac.  rac. (                          42 ; serial (d. adams)                          3H ; refresh                         15M ; retry                          1W ; expiry                          1D ) ; minimum @          IN   NS     rac. rac       IN   A localhost                     IN A rac2                          IN A rac-vip                       IN A rac2-vip                      IN A rac-cluster-scan              IN A rac-cluster-scan              IN A rac-cluster-scan              IN A
3.content of :- $TTL 86400 @        IN     SOA    rac.  rac. (                          42 ; serial (d. adams)                          3H ; refresh                         15M ; retry          …

direct path reads

To resolve the direct path reads wait event :-

Please check the below views :-

V$SESSION_EVENT ->  to identify sessions with high numbers of waits
V$SESSTAT ->  to identify sessions with high "physical reads direct" (statistic only present in newer Oracle releases)
V$FILESTAT ->  to see where the IO is occurring
V$SQLAREA ->  for statements with SORTS and high DISK_READS (which may or may not be due to direct reads)

Solution approcah :-

If the file indicates a temporary tablespace check for unexpected disk sort operations.
Ensure Parameter DISK_ASYNCH_IO -> is TRUE .
Ensure the OS asynchronous IO is configured correctly.
Check for IO heavy sessions / SQL and see if the amount of IO can be reduced.Better approach will be to look at the sql query that need to be tuned and need to run in parallel .
Please check with ASH reports to see the all the queries which have this particular wait event .
Ensure no disks are IO bound.

And in the last , Please tune the disk_…

Significant Virtual Memory Paging on Linux When None is Occurring in ADDM Reports

There will be  Significant Virtual Memory Paging on Linux When None is Occurring in ADDM Reports.

There may be following message in the ADDM report:

From  the ADDM report

FINDING 1: 100% impact (48628 seconds)
Significant virtual memory paging was detected on the host operating system.

RECOMMENDATION 1: Host Configuration, 100% benefit (32719 seconds)
ACTION: Host operating system was experiencing significant paging but
no particular root cause could be detected. Investigate processes that
do not belong to this instance running on the host that are
consuming significant amount of virtual memory. Also consider adding more
physical memory to the host.

First, review the following bugs which incorrectly show large swapping statistics that may cause incorrect ADDM message as per
above message.  And if applicable, apply the bugs.

For,  for Linux:

Note:12347332.8 Bug 12347332 - V$OSSTAT / ADDM incorrectly shows very large swapping/paging stats