Oracle Database Upgrade Manually from 12.1 to 19.3

This article provides an overview of upgrading an existing non-CDB database from Oracle 12c to Oracle 19c. Upgrades can be very complicated, so this is highly recommended to read the oracle provided manual and test thoroughly before considering an upgrade of a production environment.

Oracle Database Upgradation Manual – Read More.

Upgrade Path for Oracle Database 19c:

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Upgrade Oracle Enterprise Linux (OEL) 6 to OEL 7

In this article, we will discuss how can upgrade Oracle Linux from 6 to 7 on VM. We are planning to upgrade Oracle Database to 19c. Database server’s OS is OEL 6.8 but oracle database 19c is not certified on OEL 6.8. So need to upgrade OS from version 6.8 to 7.6.

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How Oracle Database Processes DML Internally

Result set rows can be fetched either a row at a time or in groups.

In the fetch stage, the database selects rows and, if requested by the query, orders the rows. Each successive fetch retrieves another row of the result until the last row has been fetched.

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How Oracle Database Process Select Query Internally

This topic will describe how Oracle works internally with Index and Full Table Scan.

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V$ View & Data Dictionary View on Oracle

Dynamic Performance (V$) Views: The Oracle Server contains a set of underlying views that are maintained by the server and accessible to the database administrator user SYS. These views are called dynamic performance views because they are continuously updated while a database is open and in use, and their contents relate primarily to performance.

Data Dictionary View: Data dictionary tables are not directly accessible, but you can access information in them through data dictionary views. To list the data dictionary views available to you, query the view DICTIONARY.

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Oracle Real Application Cluster (RAC) Important Components

In this topic, I will demonstrate Oracle RAC components.

  • VIP IP
  • SCAN Listener
  • Cache Fusion
  • Cluster Interconnect
  • RAC 2-way Global Cache Transfer
  • RAC 3-way Global Cache Transfer
  • Cache Coherency
    • Global Cache Services (GCS)
    • Global Resource Directory (GRD)
    • Global Enqueue Services (GES)
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After Revoked Tablespace Quota From User in Oracle

In topic, I will descript how Oracle handle once we revoke tablespace quota from user. Once blocks assigned to a segment, even after revoked the Tablespace quota and deleted records from table, all allocated block will remain mapping with segment until we released block by using Shrink.
This is the one good reason to release the space once we delete lots of records from a segment.

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Unused or Drop Column? Which option should use?

Sometimes DBA got request to drop the table’s columns. Oracle has following options to complete this task.

In this article, I will discuss which option is more appropriate for big size of table. For small table, even physical delete will not take take much time or resource.

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Oracle RAC Cache Fusion

Until Oracle 8i released, Oracle Introduced Parallel Server on Oracle 6i version. Oracle Introduced Real Application Cluster concept on Oracle 8i version. Oracle Cache Fusion is one of the important component in Oracle RAC environment.

What is Cache Fusion:

Oracle RAC is composed of two or more instances. Oracle RAC Cache Fusion is mechanism to transfer data blocks from the one instance’s buffer cache to another instance’s buffer cache across the cluster interconnect. When a block of data is read from disk by an instance within the cluster and another instance is in need of the same block, it is easy to get the block image from the instance which has the block in its SGA rather than reading from the disk. Transfers across this private network are in order of magnitude better than disk I/O activity and they help Oracle RAC performance.

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Oracle Database 19c Installation On Oracle Linux 7.1

I will describe the installation process of Oracle 19c (19.3) Database on Oracle Linux 7.1 on VM.

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