Swapping space critical on DB servers

[Fenglin]

Hi Aneesh

How did you deduce that more swap memory is needed? and how to do it?

Thanks in advance
Feng Lin

[Dennis Handly]

>How did you deduce that more swap memory is needed?

Possibly by using the old rule of thumb of 2 X the size of RAM??

>total 25009 20623 4386 82%

You have 4 Gb free. If you aren't planning to start more processes, you may have enough.
"swapping space critical": This may mean you are low on swap.

[Johnson Punniyalingam]

As adviced by <> if you are not planning to start more process - you have enough swap space.

If You intend to start more process, you can increase you swap space

Are you familiar with "LVM" commands ..?

[Johnson Punniyalingam]

Using swapon command


Create the logical volume for your secondary swap:

# lvcreate -L 128 /dev/vgXX

NOTE: "-L 128" is the size of desired swap


Verify the logical volume:

# lvdisplay /dev/vgXX/lvolXX

Use SAM to declare your new secondary swap or use the command line:

# swapon /dev/vgXX/lvolXX

Verify it has been added in "/etc/fstab" when using SAM, or add it manually when using the command line.

Example:

/dev/vgXX/lvolXX . swap defaults 0 0

[Aneesh Mohan]

Hi,

In dedicated server mode ,the UGA is allocated in the PGA and single session can demand more virtual memory depends upon the transaction/statement and number of memory objects .If you executed heavy sorting queries or highly memory intensive queries you need to have more virtual memory .
As per swa info o/p.
Your system had used more than 4GB swap memory (page out) .It indicates your system might have experienced low on physical memory than the threshold and triggered paging out operation using LRU., presumably if we have sufficient physical memory we shouldn`t need to page out ever
There are cases where the paging out can be caused by file system buffers also quite a bit.
vmstat utility gives you â poâ and â srâ rate , if it is rising steadily during your normal operation you can decide to add more physical memory.
If your system is experiencing memory pressure then there are chances of paging out critical parts of the SGA is never good unless you use lock_sga instance parameter .

Regards,
Aneesh

[Fenglin]

Thanks to all for your replies.

We just did a data migration cutover. Before the data migration, there was no swap space critical alerts on the DB server. After the data migration, we start receiving the alerts. Obviously, we want to know what is causing the additional memory required.

I realise that we receive the alerts when there are 4 or more ORACLEISVCEPS processes running on the DB server. There were some changes to the schema ISVCEPS(now, it exists both the old and the new). We did some deployment changes as well.

Based on your DB expertise, are you able to help me identify where the root cause is?

[Michael Steele_2]

Please provide

a) Total physical memory size
b) oracle SGA size
c) ipcs -mob
d) vmstat 5 5
e) UNIX95=1 ps -ef -o vsz,pid,ppid,state,chan,comm
f) UNIX95=1 ps -ef -o pcpu,pid,ppid,state,chan,comm

[Michael Steele_2]

g) swapinfo -tam
h) Append to - UNIX95=1 ps -ef -o .... | sort -rn | head 15
i) exact error messages and source

[Fenglin]

Attached are the results.

Best regards
Feng Lin

[Michael Steele_2]

Hi

You've got 2 GB of Total Memory and an SGA 1.8 GB and 5.5 GB of shared memory, 110 MB of free memory 5.0 GB Active Memory?????

Please run this command and verify your Physical memory size

Glance, m for memory, look around at the bottom of page for actual size
-or-
grep Phy /var/adm/syslog/syslog.log
-or-
dmesg | grep Phy

One of this should verify Total Memory.
#######################
Note: For sure you are out of swap. 83% Total means its time to add some more.

Also, you paged out once. 83% swap, not unexpected or unusual

The UNIX95 commands are too big. Please rerun them with appended to the end

| sort -rn | hear -15

Note: 25 GB swap.

Dude, you got a lot more RAM than you think.