OS paging versus PRIV mode

[Former Member]

Hi Experts,

We always found there are users using more than 2GB for transaction, so we did the below changes in our system to avoid fragmentation and paging of extended memory

1.Instead of allowing a process to grab 2 GB of (shared) extended memory before going in PRIV mode, the limit will be reduced to 800 MB.As a counterpart, private heap memory limits will be increased from 2 GB to 3,2 GB.

2.So total maximum memory per user is still 4 GB, but high memory users will have to "pay for it"

3. The advantage is that private memory is given back to the operating system once the transaction is finished, whereas shared extended memory is never given back (by design).

our assumption is we would never see MaxUse of extended memory > 12 GB in future.so users are allowed getting PRIV mode from time to time in our production.

But now we are getting some other problem.We are getting too much OS paging (according SE06)

Just what to confirm here with the experts

1. This PRIV mode of the WP uses the needed memory exclusively, the WP will not be interrupted and so uses much CPU, so Priv mode causes the high OS paging.?

2. Does SE06 includes the OS paging with IO?

3. What are the other options we do have to reduce this high paging

Please guide

Thanks,

Jansi

[former_member550979 · Accepted solution]

Hi,

more information is needed:

- Is a database running on the same host - if yes: Which one? What are the parameters (Buffers,...)?

- Are there more DIs? Do they have the same problem?

- Which OS is used?

- Please have a look at st02 - detailed analysis menu - storage and note the values for

"Storage shared between work processes - Total"

"User storage for all work processes"

"Size of Extended Memory"

"Maximum heap area for all work processes"

- What are the parameters for file system caching on that server?

The possible options depend on the root cause - processes which are consuming more than 2 GB are normally not well tuned or select-conditions are unsufficient.

Best regards

Andreas

[former_member182313]

1. This PRIV mode of the WP uses the needed memory exclusively, the WP will not be interrupted and so uses much CPU, so Priv mode causes the high OS paging.?

PRIV mode or not, paging will occur if there is not enough memory. Even in PRIV mode, WP will be interrupted at O/S level if O/S follows round-robin method(UNIX) of assigning tasks to CPU.

2. Does SE06 includes the OS paging with IO? I assume yes.

3. What are the other options we do have to reduce this high paging

Here are options:

1) Tune ABAP programs.

2) Add more memory. How much (AVG)free/min/max memory you see every hour in st06? If you see really low memory almost every hour every day, then I would either try to add more memory or tune ABAP programs or review memory allocation to different components(DB/SAP system(s)/Any other application/Java if dual stack) more carefully and revise allocation if needed or perform all of the above.

Bala