SQL Performance (MOSC)

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performance problems in 12c

edited May 31, 2018 8:50AM in SQL Performance (MOSC) 14 commentsAnswered ✓

Hi,

We recently upgraded from 11g to 12c on a very strong hardware with 120 CPUs and 750GB RAM

SGA = 240 GB

db_cache_size = 116 GB

shared_pool_size = 22 GB

DB is 2 node RAC.

We are observing that lot of queries are running now with very bad execution plan on this hardware, doing wrong cardinality estimates most of the times and using MERGE JOIN CARTESIAN alot.

Same queries run fine on a different DB on separate hardware with much less memory and sga size. Both DBs have same data and same stats.

example bad query below

SQL_ID  8pyb9tvcb8jsj, child number 0

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