to understand the memory allocation and its usage it’s important to know how and when HANA decides to deal with the different memory areas.

Did you ever see a huge memory consumption and analyze that the root cause is not the amount of your actual CS/RS data? The root cause may be more located in the area of the heap memory. But how HANA handles this area and when it will be freed? Is the behaviour and the size normal or too big?

The basics of memory allocation are already pretty good explained in the documentation on help.sap.com , in the SPS12 administration guide, SAP HANA Memory Usage Explained or via saphanatutorial.com

For better reading of the blog I have splitted it into three more parts:

For now only the “used memory” part is interesting. May be you heard about “resident memory” (note 2081473) => this is the OS view which is a not up-to-date value in cause of the deferred garbage collection / release of memory and can’t be taken as indicator.
used memory” consists of:

  • Table Data (Row Store + Column Store + System Tables)
  • Code and Stack
  • Database Management / Working Space (heap and shared memory)

SAP HANA Used Memory
Some more details to what is behind the more interesting parts shared and heap memory:

###############
Shared memory
###############

###############
Heap memory
###############


Changes in SPS12

Besides the parameter “unload_upper_bound” there are some more things which have been changed.
Why I go deeper into this topic? For the most companies SPS12 with its 3 years support is the main release for the next 1-2 years.
Go next to Part 3: tech. changes in SPS12

So it’s important to know a bit more what was changed. All this informations are already released, but still a check for the revision is missing, which issues/bugs are affecting your DB revision. That is the reason for this list (no guarantee for completion) refering to SPS12:

Description Allocator   Note fixed in SPS11 Rev.
fixed in SPS12 Rev.
NUMA binding issues 2358255 and 2391198 122.02+
memory leak in the context of calculation scenario Pool/malloc/libhdbcalcengine* 2374935 112.07 122.04+
Row table memory leak on SPS11 and SPS12 2362759 112.06+ 122.02+
Metadata cache memory leak in SPS12

Pool/RowEngine/RSTempPage

1999997 / 2402318 122.04+
PlanViz and the plan trace memory leak Pool/planviz* 2405237 112.07 122.03+
Row store lock and version information in SPS11 and SPS12 Pool/RowStoreTables/LockTable 2391552 122.05+
Temporary row store tables Pool/RowEngine/RSTempPage 2368929 112.07 120+
Spatial data memory leak Pool/spatialcs 1999997 122.03+
High “Used memory” (see Part Heap Memory) Pool/PersistenceManager/PersistentSpace/DefaultLPA/Page 2301382 122.05+
Join Engine Query Returns Unexpected Results in Aggregation of Large Intermediate Result Sets 2403088 122.05+

After you know all the details, you still want to stay at a revision < 122.05? I think now you have enough reasons for an upgrade/update to get your needed downtimes (may be not, if you use DBSL suspend feature and zero downtime maintenance) from your business. Take care to deactivate all workarounds which you may have activated during the time and don’t forget the workarounds for the issues which are currently not fixed in 122.05.

At the end of the day it is not a wrong sizing or the huge growth of the DB which leads to a bottleneck.
Check out the main reason (follow note 2222718) and compare the affected allocators with note 1999997 for known bugs.


Appendix for more details

1999997 – FAQ: SAP HANA Memory
2301382 – High “Used memory” in Pool/PersistenceManager/PersistentSpace/DefaultLPA/Page after upgrade to HANA SPS11 or a higher SPS
2222218 – FAQ: SAP HANA Database Server Management Console (hdbcons)
SAP HANA Memory Usage Explained
2222718 – HANA Troubleshooting Tree – High Memory Consumption
2127458 – FAQ: SAP HANA Loads and Unloads
2395937 – SAP HANA SPS 12 Database Maintenance Revision 122.05
2325090 – SAP HANA DB: Known issues detected in SPS12
HANA Academy Youtube Channel
whats new with sap hana sps12 by sap hana academy

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2 Comments

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  1. Daniel Klein

    Thank you for your efforts. Memory monitoring/finetuning is an important task easily forgotten, especially in times of S4/HANA.

    By reading the headline “Changes in SPS12” I was expecting mostly SPS<12 to SPS12 comparisons, but it seems the most fixes are for maintenance revisions. Again, sadly we could not trust the DSR-revision (122.00) which claimed to be stable. There are 92 (!) known issues in SPS12 according to https://launchpad.support.sap.com/#/notes/2325090

    I would like to read more recommendations of yours in your blogs concerning memory setup/management and automated monitoring.

    Regards
    Daniel

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    1. Jens Gleichmann Post author

      Hi Daniel,

      thanks for the feedback. You mean functional or technical/parameter changes prior SPS12 compared to SPS12? For functional changes there are already pretty good sources available. I recommend the HANA Academy Youtube Channel or the blog posts.
      Technical changes such as new parameter or new memory handling are only documented in various notes.This could be the next part of these series, if there is enough interest.

      The prior releases had also similiar amount of known issues
      e.g. SPS11: 128 issues (note 2265103), SPS10: 123 issues (note 2184212) and SPS09: 124 issues (note 2093754). So the 92 ones are pretty good 😉

      Regards,
      Jens

      (0) 

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