My Daily Learnings about Oracle Technology

Discussion about startup sequence and service features of Grid InfraStructure Services This is a three part series which discusses exhaustively about 11gR2 GRID Infrastructure Services. Assuming that we are discussing about a unix like operating system or a linux. Once the OS finishes the bootstrap process, it reads the /etc/initab file via the initialization daemon init.d At the end of the file "/etc/inittab" is a line, which looks something like this "h1:35:respawn:/etc/init.d/init.ohasd run > /dev/null 2>&1 </dev/null" the above line inidicates the initialization daemon to trigger the Oracle High Availability Services Daemon. OHASD is of two types - OHASD for cluster(also known as crs) - OHASD for non-rac environments(also known as has) ; has - high availability service Oracle Restart is bundled with GI software/Clusterware which is usually installed as part of non-rac environment installation OHASD starts 3 com...

How to Use DBMS_XPLAN.DISPLAY_CURSOR to examine execution plans As you all know we can get to know the execution plan of the optimizer in several different ways. In this post, we are going to examine, DBMS_XPLAN.DISPLAY_CURSOR which shows the actual/running execution plan of a SQL query. DBMS_XPLAN is a package inside SYS schema. DISPLAY_CURSOR is a function inside the package. Let us see how we can use the above to benefit us in fixing problematic and long running queries. SELECT * FROM table(dbms_xplan.display_cursor());  The SQL Statement executed above will pick the SQL that has been last executed in the current session. It returns the SQL_ID, the child Number, the Plan Hash Value, the Execution Plan. The * in the execution plan as indicated will have the predicate information below the execution plan. Sample DBMS_XPLAN.DISPLAY_CURSOR output The Rows column & the Time Column in the above plan are only the estimated Values for each operation as indica...

Distribute for Service: A New Feature in (12cR2) Today, we are going to understand a new feature introduced in Oracle Database 12cR2. The feature is called, Distribute for Service. What this new feature allows you to do, is to limit the objects/tables getting populated into a in-memory column store in a RAC environment. By Default in a RAC environment, a table or an object is broken up into pieces and each piece is populated into a in-memory column store across the RAC cluster. If you do not want to allow this, and may be you want to have the application access a specific RAC node, where this table as a whole is populated, then you can use distribute for service feature combined with service specific features of Oracle RAC environment. Let us consider a 2-node RAC environment which has 3 services. ( IM1, IM2 & IM_ALL ) IM1 runs on only node 1 IM2 runs on only node 2 IM_ALL runs on node1 and node2 There is a global view called, "gv$im_segments...