Trace Flag 834 And Columnstore Tables

Joe Obbish shows how trace flag 834 can solve a bottleneck when inserting into tables with clustered columnstore indexes:

In my experience, when we get into a situation with high memory waits caused by too much concurrent CCI activity all queries on the server that use a memory grant can be affected. For example, I’ve seen sp_whoisactive run for longer than 90 seconds.

It needs to be stated that not all CCIs will suffer from this scalability problem. I was able to achieve good scalability with some artificial tables, but all of the real target tables that I tested have excessive memory waits at high concurrency. Perhaps tables which require more CPU to compress naturally spread out their memory requests and the underlying OS is better able to keep up.

Read the whole thing, and also check out Lonny Niederstadt’s comment as it adds pertinent information about TF834.

Related Posts

Clustered Columnstore and Azure SQL DB

Arun Sirpal takes us through online clustered columnstore index creation in Azure SQL Database: What tier do you need to create one of these things? Let’s see. CREATE CLUSTERED  COLUMNSTORE INDEX cciSales ON [SalesLT].[ProductModelProductDescription] WITH ( ONLINE = ON ) But I get this message, Msg 40536, Level 16, State 32, Line 1‘COLUMNSTORE’ is not […]

Read More

Creating a Columnstore Index

Monica Rathbun shows a scenario where creating a clustered columnstore index can make data retrieval much faster: Using AdventureworksDW2016CTP3 we will work with the FactResellerSalesXL table which has 11.6 million rows in it. The simple query we will use as a demo just selects the ProductKey and returns some aggregations grouping them by the different […]

Read More

Categories

March 2018
MTWTFSS
« Feb Apr »
 1234
567891011
12131415161718
19202122232425
262728293031