"Database Management" category under HANA Used Memory

[Former Member]

I can't seem to find any detailed documentation on what exactly the category "Database Management" means and what it is comprised of.

When I go to "Open Memory Overview" I see under SAP HANA Used Memory a category for Code and Stack, Table Data and Database Management.  On my appliance, Database management is using up 61 gigs of memory.  Should this be consuming that much memory?  Should I expect it to grow over time?  Can I reduce the amount of memory being eaten up in this space or limit it?

Thanks in advance.

[Former Member · Accepted solution]

I would recommend you to run SQL: "HANA_Memory_TopConsumers" (SAP Note 1969700) with AREA = 'HEAP' in its "Modification section". This will show you the actual top heap allocators which most likely contribute to the "Database Management" portion. SAP Note 1999997 then explains individual heap allocators in detail.

[Former Member · Accepted solution]

Excellent Martin!  Those are some valuable queries found in that note! 

I've isolated the larger memory hogs in the heap area, with Pool/malloc/libhdbljitbase.so being the biggest at 15gb.  Anyone know what this might be?  Again, not alot of documentation to be found on this specifically.

Thanks for the link to the Note.  I'll be sure to explore more of those queries in my spare time.

Jeff.

[Former Member · Accepted solution]

I have never come across a significant memory allocation related to Pool/malloc/libhdbljitbase.so. This allocator is a generic fallback allocator for allocations done by the library libhdbljitbase.so which is related to the L language and AFL. 15 GB is not really much, so it is not necessarily a problem. If it continues to rise there is a chance that you hit a memory leak. Then I would recommend you to open an incident with SAP.

[TomCenens · Accepted solution]

Seeing Martin's comment on the memory leak, makes me want to ask what Revision you are running on?

Best practice would be to go for Datacenter Service Point (DSP) Revision of SAP HANA which is currently 96 ~ reference SAP Note 2021789 - SAP HANA Revision and Maintenance Strategy to avoid such issues

Lately, (9x revisions < 96) have been a bit rocky from time to time, you'll find some notes to back that statement up if you search for them

[Former Member · Accepted solution]

Thanks again Tom.   We are currently on revision 82 with no current plans to upgrade to Rev 9x. And for the record, this thread has been in reference to our Production on premise appliance w/ 500 GB memory.

Jeff.

[TomCenens]

Hi Jeff

The database can use up to half the amount of memory (roughly) to perform database management tasks / temporary computations.

Check out:

https://hcp.sap.com/content/dam/website/saphana/en_us/Technology%20Documents/HANA_Memory_Usage_SPS8....

You should check out in more detail, what's consuming memory within that part in order to make any call on whether or not it's normal behavior or something should be investigated. Hard to tell just based on a statement of what's in use.

Best regards

Tom

[Former Member]

Thanks alot Tom.  I did have a look at that document prior to my post and I couldn't find the details of Database Management memory.  It is definately a great document for everyone to have though.