11iv3 with Oracle 11g excessive swapping, memory only 44% used (673 Views)
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Trusted Contributor
Alan Casey
Posts: 368
Registered: ‎08-19-1997
Message 1 of 7 (673 Views)

11iv3 with Oracle 11g excessive swapping, memory only 44% used

We have 8GB of memory

Since running oracle 11g on this server we are getting excessive swapping and had to add more device swap

the database is not responding well and even the command prompt is hanging on the OS.

 

Any ideas?

 

# swapinfo
             Kb      Kb      Kb   PCT  START/      Kb
TYPE      AVAIL    USED    FREE  USED   LIMIT RESERVE  PRI  NAME
dev     8388608 1959628 6428980   23%       0       -    1  /dev/vg00/lvol2
dev     16777216 1928812 14848404   11%       0       -    1  /dev/vgsan/swap3
reserve       - 6248632 -6248632
memory  7948276 1894712 6053564   24%
# vmstat 1 1
         procs           memory                   page                          
    faults       cpu
    r     b     w      avm    free   re   at    pi   po    fr   de    sr     in
    sy    cs  us sy id
    2     4     0  1613999   73551   11    0   464  588    29    0  5531   1536
 73155  2223  13  5 82

Honored Contributor
Patrick Wallek
Posts: 13,771
Registered: ‎06-21-2000
Message 2 of 7 (670 Views)

Re: 11iv3 with Oracle 11g excessive swapping, memory only 44% used

How are you determining that only 44% of RAM is being used?

 

8 GB of RAM seems awfully small for 11iv3 and Oracle 11g.  I would do a minimum of 16GB and would go to 32 GB if I could afford it.  This would enable larger SGA sizes as well, which could improve DB performance.

Trusted Contributor
Alan Casey
Posts: 368
Registered: ‎08-19-1997
Message 3 of 7 (663 Views)

Re: 11iv3 with Oracle 11g excessive swapping, memory only 44% used

we only have 8GB of memory but this database ran on 4GB until recently

The Oracle minimum is 1GB and the SGA is set to 3GB

 

I have uploaded some more data I had to collect for the call I have open with support

Acclaimed Contributor
Dennis Handly
Posts: 25,049
Registered: ‎03-06-2006
Message 4 of 7 (628 Views)

Re: 11.31 with Oracle 11g excessive swapping, memory only 44% used

[ Edited ]

>memory only 44% used

>we are getting excessive swapping and had to add more device swap

 

It seems hard to believe that 44% and the vmstat PO output.  Did you measure these at the same time?

From your attachment, it seems you did.  But you seem to have a real variable load.

 

As Patrick said, you need more RAM.  You seem to have allocated 6 GB of device swap.

Honored Contributor
chris huys_4
Posts: 347
Registered: ‎09-27-2004
Message 5 of 7 (607 Views)

Re: 11iv3 with Oracle 11g excessive swapping, memory only 44% used

The system is using 95% of physical memory. vmstat 78000 free pages of 4k per page , equals to around 400Mbyte of free memory. On a 8Gbyte RAM system, that means 5% is left over. Which basically means the system is close to trashing.

 

The memory line in the swap info output has nothing to do with how much memory the system has left. Its a swaprelated information.

 

 

Honored Contributor
Bill Hassell
Posts: 14,205
Registered: ‎05-29-2000
Message 6 of 7 (596 Views)

Re: 11iv3 with Oracle 11g excessive swapping, memory only 44% used

>> we only have 8GB of memory but this database ran on 4GB until recently

 

What the database did in the past is only relevant if the DBAs made *no* changes to schemas or SGA or SQL procedures. The fact that the system is running out of RAM (and therefore paging very badly) means that something has dramatically cheanged. It may not be Oracle, it could be JavaJunk that has run away. But the system is struggling to accomodate the application memory demands.

 

I would start by identifying memory usage by programs. Paste this command exactly into a shell prompt:

 

UNIX95=1 ps -e -o vsz,pid,ppid,args | sort -rn | head -20

 

The first column is KBytes for the program's address space, so the biggest programs wil sort to the top of the list. What you are looking for are unusual values for some programs.

 

Take a look at shared memory with:

 

ipcs -bmop

 

Again, unusually large values that are not expected may point to a runaway program.

 

When the pagout rate hits 3 digits (more than 99), the OS will be crippled as it tries to rearrange memory and processes.  A high paging rate will destroy performance. The only fix without changing the programs is to double, or triple the amount of RAM.

Honored Contributor
Eric Antunes
Posts: 1,931
Registered: ‎06-15-2003
Message 7 of 7 (577 Views)

Re: 11iv3 with Oracle 11g excessive swapping, memory only 44% used

Hi,

 

For 11.2 database, you only need 1.5 times RAM of swap (see Metalink Note ID 169706.1): "Between 4 GB and 8 GB then 2 times RAM. Between 8 GB and 32 GB then 1.5 times RAM. More than 32 GB then 32 GB RAM". So it seems you may have to much swap. I'm not sure about that, but I think it would be faster on your internal disks (/dev/vg00) than on some SAN...

 

I also think 8 Gb of RAM is a little short:

 

1Gb for HP-UX

3 Gb for Oracle DB

2-3 Gb? for pga_aggregate_target (Process Global Area)

 

Check your database parameters with the following query (as system or sysdba):

 

select *
from v$parameter
where (name like '%sga%' or name like '%pga%')
and isdeprecated <> 'TRUE'

 

 

 

 

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