Translation Table in Hana

Pool/JoinEvaluator/TranslationTable

Translation tables are created for caching join column entries of join engine queries. The number of translation tables that are kept in memory is determined by the the following parameter in indexserver.ini:

[joins]
translator_cache_size = n

The default value is 2000. In order to verify how many translation tables currently exist in the system, the following statement can be used:

select * from sys.M_DEV_JOIN_TRANSLATION_TABLES_ order by TRANSLATION_TABLE_MEMORY_SIZE desc

This statement sums up the memory usage of those tables:

select host, port, transtable_memory from sys.m_dev_joinengine_

HOST    PORT    TRANSTABLE_MEMORY
vadbliy   30,203  4,071,520,964


In case of excessive memory usage for this allocator, the parameter can be set to 500 as a starting point. Lowering the value can have an impact on query performance though. However, in live systems where this was done, no negative side effects were observed sofar.