OracleNotes

Category: TidBits

  • Oracle Tidbits – September 2016

    Oracle TidBit
    Oracle TidBits

    “Oracle *daily* TidBits” (#oratidbit) published at https://www.facebook.com/oraclenotes on weekdays in September 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 VALIDATE DATABASE command in DGMGRL (Data Guard Command Line Interface) shows the database role and if the database is ready for switchover and failoer.
    #oratidbit Oracle Data Guard far sync instance is a redo transport destination that accepts redo from a primary database and forwards that redo to one or more redo destinations in the configuration.
    #oratidbit Oracle Virtual Private Database (VPD) enables you to dynamically add a WHERE clause in any SQL statement that a user executes. The WHERE clause filters the data the user is allowed to access, based on the identity of a user.
    #oratidbit An Oracle Data Guard broker configuration can contain up to 253 members, including one primary database and a combination of standby databases and far sync instances that receive redo directly from the primary database.
    #oratidbit If a standby database is an Oracle RAC database, only one instance of the Oracle RAC database can have log apply services running at any time. This instance is called the apply instance. If the apply instance fails, the broker automatically moves log apply services to a different instance; this is called apply instance failover.
    #oratidbit OPTIMAL_LOGFILE_SIZE column in V$INSTANCE_RECOVERY is populated when FAST_START_MTTR_TARGET init parameter is set. Your online redo log file size should be at least OPTIMAL_LOGFILE_SIZE.
    #oratidbit Oracle ASM natively stripes its content across the ASM members (storage devices). ASM uses two types of striping: coarse-grained striping allocates capacity across ASM disk group member’s round-robin; fine-grained striping, (used by default only for the control files) divides the ASM members into groups of eight, allocates an AU on each, and stripes the newly created data at 128 KB across the eight members, until the AU on each of the members is full.
    #oratidbit User-created tablespaces are encrypted by default on Oracle Database Cloud #DBaaS. Tablespaces created during database deployment are not encrypted.
    #oratidbit To create a RAC database on Oracle Database Cloud, you must choose “Extreme Performance” for “Software edition” and Choose Yes for “Setup RAC”.
    #oratidbit Use raccli utility on Oracle Database Cloud #DBaaS to backup, recover, change backup and security configuration, and patch RAC instances.
    #oratidbit Use dbaascli utility on Oracle Database Cloud #DBaaS to perform administrative operations such as change password of SYS user, check status and switchover/failover in Dataguard configuration, patch database deployment, database recovery, etc.
    #oratidbit In Oracle #DB12c 12.2 Container Database, you can have up to 4096 pluggable databases. In 12.1, the limit was 255.
    #oratidbit In Oracle #DB12c 12.2 container database, undo tablespace can be local to the PDB (new in 12.2) or can use CDB Undo known as shared undo (similar to 12.1).
    #oratidbit In Oracle #DB12c 12.2 container database, you can flashback a single PDB. In 12.1 you had to flashback the entire CDB.
    #oratidbit In Oracle #DB12c 12.2, you can failover at PDB-Level using Dataguard Broker. In 12.1 failover is at CDB level.
    #oratidbit In Oracle #DB12c 12.2, initialization parameter SGA_MIN_SIZE at PDB level guarantees minimum SGA allocation to the PDB.
    #oratidbit In Oracle #DB12c 12.2, Grid Infrastructure Management Repository can be on separate diskgroup. In 12.1 GIMR is installed on the Voting Disk diskgroup.

  • 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.