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  • Oracle Tidbits – August 2016

    “Oracle *daily* TidBits” (#oratidbit) published at https://www.facebook.com/oraclenotes on weekdays in August 2016. You will also see these tidbits, one tidbit at a time, for each page refresh on the right side of this blog as well… Hope you find these helpful to learn something new or to remind you of its existence and use…

    #oratidbit All Oracle transactions obey the basic properties of a database transaction, known as ACID properties – Atomicity, Consistency, Isolation & Durability.
    #oratidbit Oracle Database supports statement-level atomicity, which means that a SQL statement is an atomic unit of work and either completely succeeds or completely fails. The effect of the failure (rollback) is as if the statement had never been run.
    #oratidbit A system change number (SCN) is a logical, internal time stamp used by Oracle Database. SCNs order events that occur within the database, which is necessary to satisfy the ACID properties of a transaction.
    #oratidbit SHARING column in ALL_OBJECTS is new in 12c. In a PDB, value of METADATA LINK is a directive to get metadata from CDB$ROOT, OBJECT LINK is a directive get object from CDB$ROOT.
    #oratidbit ORACLE_MAINTAINED column in ALL_OBJECTS is new in 12c. Objects with value Y in this column must not be changed in any way except by running an Oracle-supplied script.
    #oratidbit When you request a trial subscription to an Oracle #Cloud service at cloud.oracle.com, the system automatically assigns you three roles: account administrator, identity domain administrator, and service administrator.
    #oratidbit Two types of subscriptions are available in Oracle Database as Service – Oracle Database #Cloud Service and Oracle Database Cloud Service Virtual Image.
    #oratidbit Unicode (AL32UTF8) is the character set used by database instances created in Oracle #DBaaS #cloud.
    #oratidbit Oracle Database #Cloud Database Schema Service is built on Oracle Database technology, running on the Oracle Exadata Database Machine. Service includes Enterprise Edition Database, Application Express, RESTFul Web Services and Packaged Applications Sample Code.
    #oratidbit The Oracle Database #Cloud provides complete data isolation at the database or VM and network levels. With Database Schema Service, each tenant receives a dedicated Oracle Database schema. With Database as a Service, each tenant is provided a dedicated database instance on a virtual machine.
    #oratidbit the SET NEWNAME FOR configuration in RMAN DUPLICATE can specify clauses FOR DATABASE (all files), FOR DATAFILE (only data files), FOR TEMPFILE (for temporary files) and FOR TABLESPACE (files belongin to tablespace).
    #oratidbit If the database control file is restored from backup or re-created, all accumulated flashback log information is discarded. You cannot use FLASHBACK DATABASE to return to a point in time before the restore or re-creation of a control file.
    #oratidbit Query the V$RMAN_BACKUP_JOB_DETAILS for the backup job history including backup type, status, start and end time, backup job speed, size of the backups.
    #oratidbit Hybrid Column Compression and In-Memory Column Store (IM column store) are closely related. The primary difference is that Hybrid Column Compression optimizes disk storage, whereas the IM column store optimizes memory storage.
    #oratidbit When an update occurs for a row in an uncompressed data block, only the updated row is locked. When using Hybrid Column Compression, the database must lock all rows in the compression unit if an update is made to any row in the unit.
    #oratidbit Bitmap indexes can include keys that consist entirely of null values, whereas for B-Tree indexes Oracle Database does not index table rows in which all key columns are null.
    #oratidbit Before you create a DBaaS instance on Oracle Database #Cloud (#DBaaS), you must setup an SSH public/private key pair to connect to compute node and optionally Oracle storage cloud service container to backup the database to cloud.
    #oratidbit Oracle DBaaS Monitor provides monitoring and management of the Oracle database and listener on Oracle Database #Cloud #DBaaS. DBaaS Monitor provides quick and easy access to a variety of information about the database instance running.
    #oratidbit #DBaas monitor, along with other management monitoring information, provides capabilities to start and stop database instance, open and close pluggable database, create, drop and clone pluggable database and start & stop listener.
    #oratidbit Use the oracle-dbcs-cli utility on your Linux computer to connect to Oracle #Cloud and perform a variety of life-cycle and administration operations on Oracle Database Cloud.
    #oratidbit The database services required to support Oracle #GoldenGate capture and apply must be enabled explicitly for an Oracle 11.2.0.4 or greater database by setting init parameter ENABLE_GOLDENGATE_REPLICATION=true.
    #oratidbit In Data Guard configuration, a switchover is a role reversal between the primary database and one of its standby databases. A switchover guarantees no data loss and is typically done for planned maintenance of the primary system. During a switchover, the primary database transitions to a standby role, and the standby database transitions to the primary role.
    #oratidbit In Data Guard configuration, a failover is a role transition in which one of the standby databases is transitioned to the primary role after the primary database fails or has become unreachable. A failover may or may not result in data loss depending on the protection mode in effect at the time of the failover.

  • Oracle Tidbits – July 2016

    “Oracle *daily* TidBits” (#oratidbit) published at https://www.facebook.com/oraclenotes on weekdays in July 2016. You will also see these tidbits, one tidbit at a time, for each page refresh on the right side of this blog as well… Hope you find these helpful to learn something new or to remind you of its existence and use…

    TidBit
    #oratidbit Oracle SQL Connector for Hadoop Distributed File System (Oracle SQL Connector for HDFS) provides read access to HDFS from an Oracle database using external tables.
    #oratidbit Direct upgrade to 12c is possible if your current Oracle Database is release 10.2.0.5, 11.1.0.7, or release 11.2.0.2 or later. You may directly upgrade from release 12.1.0.1 to 12.1.0.2.
    #oratidbit Starting with Oracle Database 12c, non-rolling upgrades for Oracle Real Application Clusters require Oracle Clusterware on the local node to be up and running.
    #oratidbit On Windows systems, Oracle Universal Installer (OUI) sets environment variables such as PATH, ORACLE_BASE, ORACLE_HOME, and ORACLE_SID in the registry during installation. On Linux and UNIX systems, you must manually set these environment variables.
    #oratidbit On Windows systems, Oracle Universal Installer (OUI) creates the ORA_DBA, ORA_OPER, ORA_HOMENAME_DBA, and ORA_HOMENAME_OPER groups, which are used for operating system authentication for Oracle instances. On Linux and UNIX systems, you must create the operating system groups manually.
    #oratidbit On the Windows platform, to upgrade Oracle Clusterware from releases 10.2.0.5 and 11.1.0.7 to release 12.1, you must perform an interim upgrade to 11.2.0.3 for Oracle Clusterware. After upgrading Oracle Clusterware to release 11.2.0.3, you must move the Oracle Cluster Registry (OCR) and voting disk (VDSK) to Oracle ASM.
    #oratidbit Once installed, there is no simple command to change the Oracle cluster name. On windows you must reinstall Oracle Grid Infrastructure. On Linux, the process will require cluster outage and delete all GI resources, then run $GRID_HOME/crs/config/config.sh script.
    #oratidbit The location of the Oracle central inventory on Windows is always %SYSTEM_DRIVE%\Program Files\Oracle\Inventory. When you install Oracle software on the system, OUI creates the directories for the Oracle central inventory and the Oracle Inventory group, ORA_INSTALL.
    ‪#‎oratidbit‬ Transparent Data Encryption (TDE) enables you to encrypt data so that only an authorized recipient can read it. TDE automatically encrypts data when it is written to disk, and then automatically decrypts the data when applications access it.
    #oratidbit Oracle Data Redaction enables you to redact (mask) column data, using full redaction, partial redaction, regular expressions, and random redaction. Data Redaction performs the redaction at runtime.
    ‪#‎oratidbit‬ You cannot create a Data Redaction policy for a multitenant container database (CDB). This is because the objects for which you create Data Redaction policies typically reside in a PDB.
    #oratidbit The objective in tuning an Oracle database should be to reduce the time that users spend in performing an action on the database, or to simply reduce “DB time”. Time model statistics are accessible from the V$SESS_TIME_MODEL and V$SYS_TIME_MODEL views.
    #oratidbit V$SYSMETRIC_SUMMARY shows a summary of system Metric values. The average, maximum value, minimum value, and the value of one standard deviation for the last hour are displayed for each metric item. Snapshots of this view is kept in AWR as DBA_HIST_SYSMETRIC_SUMMARY.
    #oratidbit V$SYSMETRIC_HISTORY displays system metric values available in the database, with 1 hour history. Snapshots of this view is kept in AWR as DBA_HIST_SYSMETRIC_HISTORY.
    #oratidbit In a Container database, the seed PDB is a system-supplied template that the CDB can use to create new PDBs. The seed PDB is named PDB$SEED. You cannot add or modify objects in PDB$SEED.
    #oratidbit The CREATE DATABASE … ENABLE PLUGGABLE DATABASE SQL statement creates a new Container Database. If you do not specify the ENABLE PLUGGABLE DATABASE clause, then the newly created database is a non-CDB and can never contain PDBs.
    #oratidbit If you start a database instance using the server parameter file (spfile) with the ORACLE_BASE environment variable set, then its value is automatically stored in spfile. If you unset the ORACLE_BASE environment variable and start the instance again, then the database uses the value of the Oracle base directory stored in spfile.
    #oratidbit If you have set ORACLE_BASE for the oracle user during installation, then Oracle Universal Installer creates the Oracle Inventory directory one level above the ORACLE_BASE in the path ORACLE_BASE/../oraInventory.
    #oratidbit For job separation, Oracle RDBMS installation lets you have many OS groups – OSDBA and OSOPER are standard groups. Extended group includes OSBACKUPDBA (backups), OSDGDBA (Data Guard), OSKMDBA (Key Management).
    #oratidbit Oracle Grid Infrastructure for a standalone server includes Oracle Restart and Oracle Automatic Storage Management.
    #oratidbit The orainstRoot.sh script must be run if this is the first time you are installing Oracle software on your system. orainstRoot.sh creates the inventory pointer file (/etc/oraInst.loc).