Oracle RAC One Node, introduced in Oracle Database 11g Release 2 (11.2.0.2), is a single instance of an Oracle RAC-enabled database running on one node in a cluster. It lets you consolidate multiple databases onto a single cluster while providing high availability benefits of failover protection to the single instance databases. Oracle RAC One Node databases can be configured to…
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At times, we might need to duplicate a production pluggable database to a Past Point in Time without disturbing the production database itself, in order to: View the data in the Production Database (PDB) as it appeared then Perform testing Generate reports, etc. Duplication of a PDB slightly differs from that of a non-CDB. In order to duplicate the PDB, an… Read more
Recently I wanted to create a policy managed database in my 12.1.0.2 flex cluster setup, but free servers are not available. Hence I had to unregister an administrator managed RAC database (amdbh12) to make the servers available. Having completed my testing, I dropped the policy managed database and then wanted to drop the database amdbh12 using DBCA… Read more
Introduction Oracle Database 10g Release 1 introduced Automatic Storage Management (ASM), a new framework for managing Oracle database files. ASM provides a foundation for highly efficient storage management with direct I/O, redundancy, striping and load balancing. Files stored on ASM are evenly distributed across disks in a disk group and mirrored according to the policies defined in the disk grou… Read more
Cloning of a Pluggable Database (PDB) in Oracle Multitenant is a great feature and is very useful. Oracle Database 12c Release 1 has introduced various enhancements to the cloning of Pluggable Databases to overcome the limitations imposed by the initial release of Oracle Database 12c (12.1.0.1). In Oracle 12.1.0.2c: PDBs can be hot cloned, i.e. you don’t need to put the source PDB… Read more
In the initial release of Oracle 12c (12.1.0.1c), a non-Container Database (non-CDB) could be converted to a pluggable database (PDB) using any of the following methods: Using DBMS_PDB Using datapump (expdb, impdp) Using GoldenGate replication The 12.1.0.2 patchset has introduced the ability to clone a remote non-CDB as a PDB directly over the network. Remote Cloning of a Non-CDB is a… Read more
Offline backups (also known as Cold or consistent backups) are taken when the database is in a consistent state, i.e. the database has been shut down with the SHUTDOWN NORMAL, SHUTDOWN IMMEDIATE, or SHUTDOWN TRANSACTIONAL commands. As part of a consistent shutdown, redo has been applied to the data files and the System Change number (SCN) in the data f… Read more
As data in tables is updated and / or deleted, pockets of empty space can be created, leading to fragmented free space. This free space is wasted space as it is insufficient to hold new data. Moreover, it can impact performance of the database as a higher number of sparsely-populated blocks need to be visited. Oracle 11g introduced online segment… Read more
In an earlier article, I discussed Automatic big table cache (ABTC) which is a new feature introduced in Oracle Database 12.1.0.2c. Automatic big table cache is an optional section of the buffer cache reserved for storing large objects. It tracks only big tables and automatically caches scanned big objects in big table cache thereby avoiding direct path reads. It caches… Read more
Serial direct path reads were first introduced in Oracle 11g to prevent wiping out a large number of buffers from the buffer cache by a serial large table scan. As a result, big tables accessed via serial Full Table Scans bypass the Buffer Cache and read data from the Data Files into the users’ Program Global Area (PGA). This prevents flooding… Read more
Prior to Oracle Database 12c, an ASM instance ran on every node in the cluster and ASM Cluster File System (ACFS) Service on a node connected to the local ASM instance running on the same host to fetch the required metadata. If the ASM instance on a node were to fail, then ACFS file systems could no longer be accessed… Read more
In an Oracle cluster prior to version 12.1.0.2c, when a split brain problem occurs, the node with lowest node number survives. However, starting from Oracle Database 12.1.0.2c, the node with higher weight will survive during split brain resolution. In this article I will explore this new feature for one of the possible factors contributing to the node weight, i.e. t… Read more
Oracle Data Pump was introduced in Oracle Database 10g to enable very high-speed transfer of data and metadata between databases. A salient feature of Data Pump is that it can parallelize the export and import jobs for maximum performance. However, prior to Oracle Database 11g release 2 (11.2), if a Data Pump job is executed in parallel on an instanc… Read more
In Oracle Database Releases earlier than 12c, an Automatic Storage Management (ASM) instance runs on every node in the cluster, and ASM Cluster File System (ACFS) Service on a node connects to the local ASM instance running on the same host. If the ASM instance on a node were to fail, then the shared Disk Groups and hence ACFS f… Read more
Starting with Oracle Grid Infrastructure 12c (12.1), Oracle Cloud File system (ASM Cluster File System in cluster environment) supports database files (database version 11.2.0.4 and up) in addition to general-purpose files so that entire Oracle databases can be stored inside Oracle Cloud FS. In my earlier articles I demonstrated that: For a database having its files stored on Oracle Cloud… Read more
In my last article, I demonstrated that starting with Oracle Grid Infrastructure 12c (12.1), Oracle Cloud File system (ASM Cluster File System in cluster environment) supports database files (database version 11.2.0.4 and up) in addition to general purpose files, so that entire Oracle databases can be stored inside Oracle Cloud FS. In addition, for a database with its files stored… Read more
Starting with Oracle Grid Infrastructure 12c (12.1), Oracle Cloud File system (ASM Cluster File System in cluster environment ) supports database files (database version 11.2.0.4 and up) in addition to general purpose files so that entire Oracle databases can be stored inside Oracle Cloud FS and can leverage the Advanced Data Services such as snapshots, tagging and auditing although replication and… Read more
Prior to Oracle Grid Infrastructure (GI) release 12.1.0.2, ASM Library (ASMLIB) was the only method to access storage devices by means of ASM Disks and Diskgroups. There were serious limitations to this method. The ASM disks were owned by GI home owner and both the owner and any users belonging to an operating system group designated as the OSASM grou… Read more
Prior to oracle database 12c, the procedures for converting from single-instance databases to Real Application Clusters involved following steps: Configure the control file attributes and move control file to shared storage Make the initialization parameter file entries for cluster-enabled environments and move SPfile to shared storage Create an undo tablespace for each additional instance Create redo threads for each additiona… Read more
In this article, I will demonstrate how to quickly create a standby database for a non-multitenant container database (NCDB) by plugging it as a pluggable database (PDB) into primary CDB (BOSTON). This method tremendously simplifies and speeds up the procedure to create a standby database without the need to set various initialization parameters or take backup or configure tnsnames.ora entries… Read more
