Definitely on the slow side.
The simplest rule of thumb is "if it's slower than a single block read we
probably shouldn't be using RAC".
You can see this type of repsonse (slow busy CR transfers) if you've got a
reporting node and an update node and the update node gets very busy. The
reporting node starts a "long" query and the update node has to do a lot of
work on pinning busy blocks, copying them, then making the copy read-consistent.
In a single instance I think you'd see a lot of buffer busy waits, and a lot of
"consistent gets - undo records applied" (both of which you may see on node 2
while node 1 is reporting these slow gc cr gets). Are you also seeing a lot of
"gc cr disk read" waits ?
Regards
Jonathan Lewis
________________________________________
From: oracle-l-bounce@xxxxxxxxxxxxx <oracle-l-bounce@xxxxxxxxxxxxx> on behalf
of Jack van Zanen <jack@xxxxxxxxxxxx>
Sent: 06 August 2019 01:08
To: oracle-l@xxxxxxxxxxxxx
Subject: RAC - Global Cache Transfer Times
Hi All,
Below is from AWR report and I was wondering if the CR Avg Time was on the slow
side.
Anyone have any rule of thumb as to what it "should" be?
BTW, this is during the ETL load into our DWH.
Global Cache Transfer Times (us)
* Avg Time - average time of all blocks (Immed,Busy,Congst) in us
* Immed, Busy, Congst - Average times in us
* ordered by CR + Current Blocks Received desc
CR Avg Time (us) Current Avg Time (us)
Inst No Block Class All Immed Busy Congst All Immed Busy
Congst
2 data block 26907 592 151759 942 392 9890
6391
2 undo header 2612 193 241481 1361 1361
2 others 11129 268 489014 54862 247 81818
2 undo block 201 201
Jack van Zanen
[https://docs.google.com/uc?id=0BwovDucFT1fXaEREVHNWRWZyNjg&export=download]
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