System heap value in LC10

[Former Member]

Hi,

This is related to LC 7.5 on AIX.

I go to LC10 - LiveCache Monitoring - Current Status - Memory Areas - Heap Usage.

On the right side in "Currect value" section there is a "System Heap". How does this value gets assigned. I was in impression that "System Heap" value and OMS_HEAP_LIMIT are same but it does not seem to be same.

What is the impact of "System Heap" and how can we increase it. In production it is 30% higher than OMS_HEAP_LIMIT. In test box it is same.

Please let me know if anybody has a good understanding about this issue.

Thank you.

Sume

[lbreddemann]

Hi Sume,

"System Heap" refers to the allover memory allocated by the liveCache (except e.g. the shared memory segments used for communication). So the Cache, the OMS-Heap, the User-Stacks and all the other "tiny" memory areas that are allocated when the liveCache instance gets started is included in "System Heap".

"OMS Heap" does refer to memory used to handle the objects data structure which is the core data structure in livecache. All the actual data processing of liveCache is done within this memory area.

Therefore it's pretty obvious that there will be a overhead that makes "System Heap" always larger than "OMS Heap".

OMS_HEAP_LIMIT btw. just constraints the memory used by liveCache for object handling. If there is not enough memory available on the system to provide this memory (or some other restrictions apply like address space restrictions on 32 Bit systems or ulimit-Restrictions), then liveCache routines may fail.

Hope that answers your question.

Further reading for you may be this

<a href="http://help.sap.com/saphelp_erp2005/helpdata/en/c7/b05f4288d4d142e10000000a1550b0/frameset.htm">Database Administration in CCMS: SAP liveCache Technology -> Memory Areas</a>

KR Lars

[Former Member]

Thank you for the reply.

It helped.

I have few question from this link.

One statement says - <b>If the measures described here do not improve the critical situation, increase the dimensions of the data cache</b>. How can I increase the <b>dimentions of data cache</b> or this just means that increase the data cache.

How can I find the filling level in % of OMS Heap. I know that total size is defined by OMS_HEAP_LIMIT.

How can I find that some pages of the OMS versions are displaced from the OMS heap (<b>displaced pages</b>).

I will be very helpfull if somebody can answer these.

regards.

Sume

<b></b>

[former_member229109]

-> You could increase the CACHE_SIZE liveCache parameter, see the SAP notes 408606, 719652 & 487972.

-> For SAP liveCache documentation in English: http://help.sap.com/saphelp_nw04/helpdata/en/f2/0271f49770f0498d32844fc0283645/frameset.htm

< -> Database Administration in CCMS: SAP liveCache -> liveCache Assistant ->

liveCache: Monitoring -> Current Status -> Memory Areas < -> Heap Usage !! > >

Please also review the SAP notes ::

990602 CCMS for MaxDB/SAP liveCache technology

820824 MaxDB/liveCache technology

You could use the DB Analyzer to find the bottleneck in liveCache,

the DB analyzer file DBAN_OMS_HEAP.csv will give you information on

OMS heap (such as occupancy, current size, collisions).

See the documentation at SAP documentation http://help.sap.com/saphelp_nw04/helpdata/en/f2/0271f49770f0498d32844fc0283645/frameset.htm

< -> Database Administration in CCMS: SAP liveCache ->Database Administration -> tools < from right side > -> Database Analyzer >

Thank you and best regards, Natalia Khlopina

[Former Member]

Thank for the reply.

I have read all the notes in the past including the DBAN_OMS_HEAP.csv.

My question is still same-

What is <b>dimentions</b> of data cache and how it can be increased. Does it mean that increase the data cache. I know how to increase the data cache.

How can I find the current filling level in % of OMS Heap. I know that total size is defined by OMS_HEAP_LIMIT. Please let me know if I am missing anything.

How can I find that some pages of the OMS versions are displaced from the OMS heap (displaced pages).

The above quetion are derived from the text from help.sap.com link which is pasted above.

I cannot find a very good explanation about these.

Please help me understanding the explanation.

I will appreciate your help.

Regards.

Sume.

[former_member229109]

1) "What is dimensions of data cache and how it can be increased.

Does it mean that increase the data cache. I know how to increase

the data cache."

-> As I wrote that you could increase the value of the CACHE_SIZE

< Size of the I/O buffer cache in pages > liveCache parameter.

As you know, the primary consumers of the main memory managed in

the I/O cache are the converter and the data cache.

You could monitor the data cache usage in LC10 -> liveCache:Monitoring

-> Choose Current Status -> Memory Areas -> Caches.

=> you will see the current size values in KB & pages for

I/O Buffer Cache

Data-Cache -> current size of data cache !!

Converter

Sonstiges

Catalog-Cache

Sequence-Cache

&& current data cache usage information ...

You could review the DBAN_OMS_CACHE_OCCUPANCY.csv file of the DB Analyzer

Statistics information.

Please check the Permanently Used Area of the Data Area in liveCache,

review the statistics in DBAN_FILLING.csv file, if the DB Analyzer is

Running. In case the applications are using all data created in liveCache,

For the best performance the data need to be cashed => you will define

the dimensions of your data cache ... + the history data is saved as

pages in the data cache.

And if you have problems to identify the values for the liveCache parameters

On your system => Please create the ticket to the component 'BC-DB-LVC'

For SAP liveCache documentation in English: http://help.sap.com/saphelp_nw04/helpdata/en/f2/0271f49770f0498d32844fc0283645/frameset.htm

< -> Database Administration in CCMS: SAP liveCache -> liveCache Assistant ->

liveCache: Monitoring -> Current Status -> Memory Areas < -> Caches !! >

2) "How can I find the current filling level in % of OMS Heap.

I know that total size is defined by OMS_HEAP_LIMIT. Please let me

know if I am missing anything."

As you know, the liveCache allocates memory statically as well as

dynamically. The DATA CACHE is allocated statically.

When the database instance is started, the I/O buffer cache is created in

the main memory in accordance with the size entered in the general

database parameter CACHE_SIZE.

Additionally the liveCache allocates the OMS HEAP dynamically.

The amount of the OMS HEAP memory depends on the runtime of OMS versions

and the amount of data which is used by the transactions.

The OMS heap can grow dynamically until it reaches the maximum size

specified in the liveCache parameter OMS_HEAP_LIMIT.

For SAP liveCache documentation in English: http://help.sap.com/saphelp_nw04/helpdata/en/f2/0271f49770f0498d32844fc0283645/frameset.htm

< -> Database Administration in CCMS: SAP liveCache -> liveCache Assistant ->

liveCache: Monitoring -> Current Status -> Memory Areas < -> Heap Usage !! >

So:

-> You could use Heap Usage display in the LC10.

< Currently used column -

Size of the memory actually occupied by the OMS heap

You could mark the column + click on 'Sum' => see the sum ... >

-> You could use the Memory node in the liveCache Alert Monitor under

'Space Management' for LCA connection & you will see, for example:

Heap Usage 1 % < day/time>

Heap Usage in KB 18999 KB < day/time >

***

-> Sorry, I didn't get clear on another posted questions.

Could you please give the reference to the documents or notes where you saw

those sentences.

Thank you and best regards, Natalia Khlopina

[Former Member]

Thank you very much for reply.

So basiscally increasing the dimention is nothing but increasing CACHE_SIZE. When we increase CACHE_SIZE the dimentions are also taken care of. Correct? Here is the link -

http://help.sap.com/saphelp_nw04/helpdata/en/07/f8983c6e577546e10000000a11405a/frameset.htm

It is possible that link may not take you to the requird page so I am pasting the contents of the page. You can search the string from the message below to get to page.

The title of the page is "Monitoring the Data Cache". This is what it says -

<b>If The data cache hit rate is below 99.8%, the data cache load is 100%.

For a display of the failed accesses to the data cache, refresh the Caches display in the liveCache Assistant.

Check whether there are any long-running OMS versions. Proceed as described in Monitoring OMS Versions.

<i>If the actions described here do not improve the critical situation, increase the dimensions of the data cache</i>.</b>

My question was based on the last line which says that increase the dimensions of the data cache. I got confused with this statement. Please let me know if it is anything different.

I was able to find the % of the OMS_HEAP. I should have done some research on alert monitor. Thank you for this.

My last question is that is there a quota type os concept for one seesion when it come to OMS_HEAP_LIMIT or it can occupy as much as it can until it reaches the limit of the OMS_HEAP_LIMIT. Like we have roll_extention and initial_size_MB in R/3. One is a quantity and other is total size.

Please let me know.

Once again I appreciate your help.

Thank you.

Sume

[former_member229109]

Hello Sume,

1) As you know, the main memory managed in the I/O cache used by the converter, the data cache, Sonstiges, Catalog-Cache & Sequence-Cache. Mainly -the data cache and the converter.

And you could monitor the data cache usage in LC10 -> liveCache:Monitoring

-> Choose Current Status -> Memory Areas -> Caches.

=> you will see the current size values in KB & pages for I/O Buffer Cache

After you will increase the value of the CACHE_SIZE parameter

< Please check the OS resources & value of the main memory on the liveCache server & if another applications are running on this server ... >, you need to restart the liveCache from the offline mode to activate the new value of the liveCache parameter

=> the size of the data cache in the I/O cache will be increased too < you increased the 'dimensions' of the data cache >.

2) As you know the data of each OMS version is copied to the OMS heap when it is read. Please see the liveCache parameters info at

http://help.sap.com/saphelp_nw04/helpdata/en/f2/0271f49770f0498d32844fc0283645/frameset.htm

< -> User Manual: SAP liveCache -> liveCache Parameters ->

OMS_HEAP_COUNT

OMS_HEAP_THRESHOLD

OMS_VERS_THRESHOLD >

& run dbm command 'param_getexplain <param-name>' for those parameters.

And if the running application is needed more OMS heap memory please check first the application scenario < may be the selection of the data could be changed, for example >, performance problems on the system < long running transactions in parallel ... >, check if the OMS_HEAP_LIMIT parameter set correctly for your system -> may be the value need to be increased ...

The case has to be checked first in details if you get the error - OMS_HEAP_LIMIT reached or database error '-28000' 'Operator NEW failed - out of heap memory' when LCA routine was running.

Thank you and best regards, Natalia Khlopina