2894395 - Delta Merge is not running in HANA

Delta Merge is not running in HANA.
There are lot's of alerts related to delta merge.

• Alerts

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<schema_name>.<table_name> partition 1 on xxx:3XX03 has a delta storage size of 3190MB. This exceeds the threshold value and may indicate a problem with delta merge processing.

<schema_name>.<table_name>partition 0 on xxx:3XX03 has a delta storage size of 2660MB. This exceeds the threshold value and may indicate a problem with delta merge processing.

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• Check the memory status in HANA

1) Memory Overview
- Check if the largest allocators belong to the HANA delta store.

E.g.:

Pool/ColumnStore/Delta/LeafNodes

Pool/ColumnStore/Delta/Btreeindex

Pool/ColumnStore/Delta/InternalNodes

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2) Run the following query to check the size of delta storage.

select SUM(MEMORY_SIZE_IN_DELTA) from M_CS_TABLES

SUM(MEMORY_SIZE_IN_DELTA)595,528,088,149

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3) Check which tables are occupying the memory related to delta

select top 30 * from M_CS_TABLES order by memory_size_in_delta desc

• Check the configuration of the system if the parameters related to mergedog are set to unfavorable values.

1) indexserver.ini
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[mergedog]
auto_merge_decision_func = xxxx
critical_merge_decision_func = xxxx
token_per_table = xxxx
num_merge_token = xxxx

[optimize_compression]
min_hours_since_last_merge_of_part = xxxx
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2) Check the parameters with the SQL Statement (HANA_Configuration_Parameters_*+.txt

FILE_NAME;SECTION;PARAMETER_NAME;P;DEFAULT_VALUE;CONFIGURED_VALUE;RECOMMENDED_VALUE;SAP_NOTE;CONFIG_LAYER;IMPLEMENTATION_COMMAND;UNDO_COMMANDindexserver.ini;mergedog;auto_merge_decision_func;;((DRC*TMD > 3600*(MRC+0.0001)) or ((DMS>PAL/2000 or DMS > 1000 or DCC>100) and DRC > MRC/100) or (DMR>0.2*MRC and DMR > 0.001));DMS>5000 and (DUC<0.1 or 0.05*DRC>=DUC);-- check why set --;2057046;DATABASE;ALTER SYSTEM ALTER CONFIGURATION ('indexserver.ini', 'DATABASE') UNSET ('mergedog', 'auto_merge_decision_func') WITH RECONFIGURE;;ALTER SYSTEM ALTER CONFIGURATION ('indexserver.ini', 'DATABASE') SET ('mergedog', 'auto_merge_decision_func') = 'DMS>5000 and (DUC<0.1 or 0.05*DRC>=DUC)' WITH RECONFIGURE;

indexserver.ini;mergedog;critical_merge_decision_func;;UPT > 43200 and ((MMS<10000 and DMS>1000 and TMD>86400) or TMD>604800);DMS>12000 and (DUC<0.1 or 0.05*DRC>=DUC);-- check why set --;2057046;DATABASE;ALTER SYSTEM ALTER CONFIGURATION ('indexserver.ini', 'DATABASE') UNSET ('mergedog', 'critical_merge_decision_func') WITH RECONFIGURE;;ALTER SYSTEM ALTER CONFIGURATION ('indexserver.ini', 'DATABASE') SET ('mergedog', 'critical_merge_decision_func') = 'DMS>12000 and (DUC<0.1 or 0.05*DRC>=DUC)' WITH RECONFIGURE;

indexserver.ini;mergedog;num_merge_token;;-- HANA internal --;200;-- check why set --; ;DATABASE;ALTER SYSTEM ALTER CONFIGURATION ('indexserver.ini', 'DATABASE') UNSET ('mergedog', 'num_merge_token') WITH RECONFIGURE;;ALTER SYSTEM ALTER CONFIGURATION ('indexserver.ini', 'DATABASE') SET ('mergedog', 'num_merge_token') = '200' WITH RECONFIGURE;

indexserver.ini;optimize_compression;min_hours_since_last_merge_of_part;;-- HANA internal --;0;-- check why set --;2105761;DATABASE;ALTER SYSTEM ALTER CONFIGURATION ('indexserver.ini', 'DATABASE') UNSET ('optimize_compression', 'min_hours_since_last_merge_of_part') WITH RECONFIGURE;;ALTER SYSTEM ALTER CONFIGURATION ('indexserver.ini', 'DATABASE') SET ('optimize_compression', 'min_hours_since_last_merge_of_part') = '0' WITH RECONFIGURE;---

• SAP HANA Database

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