Oracle Database In-Memory Advisor
This post describes the Oracle® In-Memory Advisor (IMA), a feature of Database 12c, and describes its benefits. This feature is available in Oracle Database version 18.104.22.168 and later.
Benefits of IMA
IMA has the following major benefits:
Faster analytical queries.
Quicker On-line Transaction Processing (OLTP) transactions.
No application changes.
Less manual work for a database administrator (DBA) to optimize database performance.
Prior to the introduction of the In-Memory Advisor, DBAs had to manually identify the tables to be placed in the In-Memory Column Store (IMCS). IMA eliminates this manual task by analyzing the analytical workload of the database and producing a recommendation report (which includes SQL commands to place the tables in IMCS).
The IMA gives specific recommendations on how to configure Oracle Database In-Memory.
The IMA produces a report identifying the objects that should be placed in Oracle Database In-Memory for maximum benefit, along with a SQL*Plus script that implements those recommendations.
IMA installation package
The installation zip file and instructions can be found in the My Oracle Support (MOS) Doc ID 1965343.1. The installation scripts install the IMA at the database level. The IMA can run on Oracle Database version 22.214.171.124, but it is recommended for Oracle Database version 126.96.36.199 or later.
The DBMS_INMEMORY_ADVISOR package provides advice on analytic workloads that can benefit from using the In-Memory option. It does this by analyzing Active Session History (ASH) and Automatic Workload Repository (AWR) data. A report is produced, as well as a script file, which contains the SQL for execution on the target databases. The script places the recommended objects in In-Memory with the suggested compression types.
IMA dual-format architecture
Traditionally, Oracle Database stores data in row format, with each transaction stored in the database as a new row, which is ideal for online transaction systems because you can quickly access all columns in a record. A column-format database stores each transaction attribute in a separate column structure and is ideal for analytics because you retrieve fewer columns. When it comes to Data Manipulation Language (DML) operations (such as insert, update, or delete), row format is efficient because it updates an entire record in one operation. If you run the same operations against a table with column format, the entire column structure of the table must be changed, which is inefficient for processing row-wise DML.
In Oracle Database 12c, data can populate tables in both an In-Memory row format and In-Memory column format. This is called dual-format architecture and provides better performance. The existing buffer cache maintains the row format, and a new In-Memory column store maintains column format. The In-Memory column store is a component of the Oracle Database System Global Area (SGA).
The following image illustrates dual-format architecture:
If you have a table that's wide and has several hundred million or even billions of rows, you can scan that table and filter it extremely quickly, even in a data warehousing environment. You can join the columns from a fact table to multiple-dimension tables with unbelievable speed. Because the data is in a columnar format instead of a row-major format, you can access the data much more quickly because you eliminate many of the intervening columns.
IMA and OLTP
IMA can be used to improve queries on a variety of OLTP and data warehouse operations and offers the following key capabilities:
Assistance with In-Memory size selection.
Recommendations for tables, partitions, and sub-partitions for a given In-Memory size.
Utilizes workload and performance data to prioritize objects.
Accommodates differences in disk and memory footprint, as well as compression ratios.
Provides workload-based cost/benefit analysis, including the following:
- Cost: Offers estimated memory-size with various compression options.
- Benefit: Offers estimated database time-reduction metrics for workload processing.
Provides an In-memory area population plan.
Provides reporting, including the top SQL benefits from any given configuration.
Allows you to vary In-Memory size to receive a specific loading plan.
Generates DDL scripts with all the tables, partitions, and sub-partitions recommended.
By using the In-Memory option, you can speed up analytical queries and OLTP as well as optimize the database performance easily with less DBA involvement. From a business point of view, businesses can benefit from better decisions made in real time, improved productivity, increased competitiveness, and lowered costs.
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