Performance in Read-only Scale out system

[former_SQLA_member1695064]

Hi,

we plan to to install a read only scale out system. Is there any experiences what are the performance effect on the root node when I execute a large statement on the copy node ? If a table on the copy node is blocked during a transaction, changes on the root node that affect a corresponding table are blocked ?

thank you

Andreas

[Breck_Carter]

> If a table on the copy node is blocked during a transaction

AFAIK that's not going to happen because the copy node is read only.

[VolkerBarth · Accepted solution]

Read-only scale-out is particularly meant to separate long-running (and "heavy-locking") queries on copy nodes from OLTP on the root node. AFAIK, the root node works somewhat as in asynchronous mirror mode of a mirror-setup, i.e. it does not wait for the copy nodes to acknowledge the successful transmission of the sent log pages to the copy node's transaction log.

Therefore, a query on the copy nodes should not at all block any transaction on the root node.

[former_SQLA_member1695064 · Accepted solution]

Many thanks

"The root node does not wait for the copy nodes to acknowledge the successful transmission". This is what I was looking for.

thank you