Why ?
With the embedded statistics server the retention time for most of the histories is already 42 days.
Nevertheless there are still a few histories with a rather small default retention time. Check ID 750 ("Stat. server tables with retention < 42 days") of SQL: "HANA_Configuration_MiniChecks" (SAP Note 1969700) reports tables where the retention time may be increased to 42 days, however there are no .ini configuration parameters as such to adjust this.
How ?
To see all the statistic server tables, associated IDs, and current retention value execute the mini check SQL "HANA_StatisticsServer_Histories_RetentionTime" which can be found in the collection of SQL statements attached to SAP Note 1969700 - SQL Statement Collection for SAP HANA.
Then you can adjust the retention time with the following command:
UPDATE _SYS_STATISTICS.STATISTICS_SCHEDULE SET RETENTION_DAYS_CURRENT=42 WHERE ID=5006;In this example we are setting the retention of the HOST_HEAP_ALLOCATORS table (id 5006) to 42 days.
Experience has shown that a retention time of 6 weeks (42 days) is a good compromise between size and analysis capabilities. Having 6 weeks of history available it is always possible to compare current issues with a time of the same load one month back (e.g. month's end closing).
Note : The standalone statistics server mainly used a retention time of 30 days. Rather than adjusting the retention time, it is recommended to switch to the Embedded Statistics Server (ESS).
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