[HANA] Cache Memory

Important SAP HANA caches

Cache	Allocator	Name in cache framework	SAP Note	Purpose	Analysis command	Configuration parameters
Adapter operations cache	Pool/AdapterOperationCache	AdapterOperationsCache		Cache for SDQ operations	SQL: "HANA_Memory_Caches_Overview" SQL: "HANA_Memory_Caches_Entries"
Calculation engine node cache	Pool/itab	CalcEngineNodeCache		Cache for cache node itabs related to planning engine	SQL: "HANA_Memory_Caches_Overview" SQL: "HANA_Memory_Caches_Entries"
Calculation engine model cache	Pool/CacheMgr/CE_ScenarioModelCache	CE_ScenarioModelCache (SAP HANA >= 2.0 SPS 03)		Cache for  calculation engine models	SQL: "HANA_CalculationEngine_CalculationScenarios"	indexserver.ini -> [calcengine] -> max_cache_size_kb
Column store statistics cache	Pool/CacheMgr/CS_StatisticsCache	CS_StatisticsCache	2124112	Scale-out cache for column store table statistics used by optimizer	SQL: "HANA_Memory_Caches_Overview" SQL: "HANA_Memory_Caches_Entries"	indexserver.ini -> [cache] -> cs_statisticscache_enabled
Currency conversion cache	Pool/TREXCache/CacheMgr/Currency/UnitConversion_RateQueriesResultCache	Currency/UnitConversion_RateQueriesResultCache	1999997	Cache for currency conversion rates	SQL: "HANA_Memory_Caches_Overview" SQL: "HANA_Memory_Caches_Entries"	indexserver.ini -> [businessdb] -> cache indexserver.ini -> [businessdb] -> cache_erp_currency_query_base_rates indexserver.ini -> [businessdb] -> cache_erp_currency_query_rates
Data statistics adviser cache	Pool/CacheMgr/DataStatisticsAdviserCache	DataStatisticsAdviserCache		Cache for CREATE STATISTICS advisory	SQL: "HANA_Memory_Caches_Overview" SQL: "HANA_Memory_Caches_Entries"
Hierarchy cache	Pool/hierarchyBlob	HierarchyCache HierarchyItabCache	1999997	Cache for hierarchical queries	SQL: "HANA_Memory_Caches_Overview" SQL: "HANA_Memory_Caches_Entries"	indexserver.ini -> [cache] -> hierarchies_transactional_cache_enabled
MDX hierarchy cache	Pool/hierarchyBlob Pool/itab (custom view attributes)	MdxHierachyCache	1999997	Cache for hierarchical MDX queries	SQL: "HANA_Memory_Caches_Overview" SQL: "HANA_Memory_Caches_Entries"	Cache activation / deactivation: indexserver.ini -> [cache] -> hierarchies_transactional_cache_enabled Time after which an entry is marked as stale (in s, default: 14400): indexserver.ini -> [mdx] -> cache_entry_timeout Action for stale entries (0 -> purge when needed, 1 -> purge immediately): indexserver.ini -> [mdx] -> cache_entry_timeout_action
MDX entity cache	Pool/entityCache	MdxEntityCache	1999997	Cache for MDX entities	SQL: "HANA_Memory_Caches_Overview" SQL: "HANA_Memory_Caches_Entries"
Metadata cache	Pool/Metadata/MetadataCache/MetadataGlobalCacheSlot		1999997	Cache for metadata (SAP HANA >= 1.00.120)	SQL: "HANA_Metadata_Cache"
Page cache	Pool/PersistenceManager/PersistentSpace/DefaultLPA/Page		1999997	SAP HANA file system cache	SQL: "HANA_Memory_TopConsumers" hdbcons 'pageaccess a'
Result cache	Pool/CacheMgr/CS_QueryResultCache[Realtime] Pool/CacheMgr/CS_QueryResultCache[TimeControlled]	CS_QueryResultCache[Realtime]CS_QueryResultCache[TimeControlled]	2014148	Cache for query results	SQL: "HANA_Memory_Caches_Overview" SQL: "HANA_Memory_Caches_Entries"	indexserver.ini -> [cache] -> resultcache_clear_reconfig indexserver.ini -> [cache] -> resultcache_enabled indexserver.ini -> [cache] -> resultcache_maximum_value_size_in_bytes indexserver.ini -> [cache] -> resultcache_minimum_query_execution_time_in_milliseconds indexserver.ini -> [cache] -> resultcache_white_list
Single value cache	Pool/SingleValueCacheBuilder		1980765	Caches values of columns with only one single value		indexserver.ini -> [cache] -> enable_single_value_caching
SQL cache	Pool/RowEngine/SQLPlan		2124112	Cache for prepared SQL statements	SQL: "HANA_Memory_SQLCache_TopConsumers" SQL: "HANA_SQL_SQLCache_Overview"	indexserver.ini -> [sql] -> plan_cache_size
System replication asynchronous buffer	Pool/PersistenceManager/DisasterRecoveryPrimary		1999880	Cache for asynchronous system replication	SQL: "HANA_Memory_TopConsumers" hdbcons 'replication info'	<service>.ini -> [system_replication] -> logshipping_async_buffer_size
System replication log replay cache	Pool/PersistenceManager/DisasterRecoverySecondary/ReplayLogCache		1999880	Cache used with system replication mode logreplay[_readaccess] for redo log data to be applied on secondary site	SQL: "HANA_Memory_TopConsumers" hdbcons 'replication info'	<service>.ini -> [system_replication] -> logshipping_replay_logbuffer_cache_size
Translation table cache	Pool/JoinEvaluator/TranslationTable		1998599	Translation table cache for join column mapping	SQL: "HANA_Heap_TranslationTables"	indexserver.ini -> [joins] -> translator_cache_size
Static result cache	Pool/RowEngine/ViewCache (<= 1.0 SPS 11) Pool/ResultCache(for cached view) (>= 1.0 SPS 12)		2336344	Static cache for query results	SQL: "HANA_Memory_StaticResultCache"	indexserver.ini -> [result_cache] -> before_analytic_privilege indexserver.ini -> [result_cache] -> enabled indexserver.ini -> [result_cache] -> total_size
Dynamic result cache	Pool/DynamicCachedView Pool/DynamicCachedView/ViewMatching		2506811	Dynamic cache for query results	SQL: "HANA_Memory_DynamicResultCache"	indexserver.ini -> [result_cache] -> enabled indexserver.ini -> [result_cache] -> total_size
Dynamic tiering relocation cache			2777465	Cache for dynamic tiering results		esserver.ini -> [row_engine] -> enable_relocation_cache

 

 

Cache Control

• Cache framework에 속한 Cache이므로 resource manager에 의해서 전체 size는 관리됨
• 개별 Cache는 Size에서 제한이 없기 때문에 만약 충분한 메모리가 주어진다면 Cache는 눈에 띄게 증가할 수 있음
  -> 정상 상태로 문제가 되지 않음
• Framework의 cache를 clear 가능 (SPS03부터)
  
  • ALTER SYSTEM CLEAR CACHE ('<cache_id>')
  • <cache_id> = M_CACHES.CACHE_ID
• Framework에 속하지 않은 Cache는 파라미터로 관리 됨
  • translator_cache_size - Translation table cache
  • plan_cache_size - SQL cache
• Cache Framework
  • Cache는 다른 방식으로 구현되며 일부는 개별적으로 조회 가능 (heap allocator sizes를 통해서)
  • M_CACHES, M_CACHE_ENTRIES를 통해 조회 가능