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We tested the Oracle Force Full Cache (FFC) feature before validating all the best practices. The Oracle FFC results were impressive, so we decided to include the results in a best practice.
Category | Oracle 19c Database |
Product | Oracle 19c |
Type of best practice | Performance Optimization |
Day and value | Day 1, Highly Recommended |
Overview
When FFC mode is implemented the Oracle server attempts to cache the full database in memory. This means all the datafiles that are related to the database are cached in memory. This reduces read latency from storage system to memory access speeds. Writes are still sent to storage to ensure durability and recovery of the database.
We highly recommend using memory technologies like FFC mode for the enterprise as AMD EPYC processors enable the PowerEdge R7525 servers to support up to 4 TB of LRDIMM. Depending on the database and its growth rate, this could support many small to medium sized systems. The benefit for business is the capability to accelerate the database by configuring a Dell EMC PowerEdge R7525 server and AMD processors with enough memory to cache the entire database.
Table 1: Virtual Machine configuration and SGA Size
Component | Oracle Baseline | Oracle Force Full Cache Mode |
vCPU | 32 | 32 |
Memory | 960 GB | 960 GB |
Disk Storage | 400 GB | 400 GB |
SGA Size | 64 GB | 784 GB |
Table 1 shows that the main distinction between the baseline and FFC mode is the SGA size. By using FFC, we wanted to fit the entire database in memory thus, the SGA size is 784 GB. We used HammerDB to create a TPROC-C workload with 5,000 simulated warehouses which generated approximately 500 GB of data, which was small enough to be loaded into the SGA.
Recommendation
New Orders per Minute for the baseline configuration reached 169,481 and 413,577 for FFC mode, which is a 244% performance improvement. Enabling Oracle FFC mode requires architecture planning to ensure the PowerEdge server has enough memory to cache the entire database. We recommend using FFC mode as a Highly Recommended, Day 1 activity.
Implementation Steps
Use the following procedure to enable FFC mode
SQL> ALTER DATABASE FORCE FULL DATABASE CACHING; SQL> ALTER DATABASE OPEN;
SQL> SELECT FORCE_FULL_DB_CACHING FROM V$DATABASE;
Additional Resources
AMD EPYC Milan Processors and FFC Mode Accelerate Oracle 244%
Oracle Database 19c: Using Force Full Database Caching Mode