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  • Oracle Tidbits – February 2017 #oratidbit

    “Oracle *daily* TidBits” (#oratidbit) published on Facebook, Twitter and Google+ during weekdays in February 2017. 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 Setting STATISTICS_LEVEL parameter to BASIC disables AWR. If STATISTICS_LEVEL is set to BASIC, you can still manually capture AWR statistics using the DBMS_WORKLOAD_REPOSITORY package.
    #oratidbit The $ORACLE_HOME/rdbms/admin/awrextr.sql script extracts AWR data for a range of snapshots from the database into a Data Pump export file (to load into another database).
    #oratidbit #db12cR2 When you take AWR snapshot at CDB level, snapshot data is stored in SYSAUX tablespace of CDB. The PDB-level snapshot data is stored in the SYSAUX tablespace of a PDB.
    #oratidbit Oracle #DB12c Feature: In-database archiving is enabled by using the attribute ROW ARCHIVAL in the CREATE TABLE or ALTER TABLE statements. Invisible column ORA_ARCHIVE_STATE is added to the table with default value 0 (not archived).
    #oratidbit DBMS_SPM PL/SQL package is used to perform SQL plan management tasks – creating, dropping, and loading SQL plan baselines. DBMS_XPLAN.DISPLAY_SQL_PLAN_BASELINE can be used to show one or more execution plans for the SQL statement.
    #oratidbit Run the asmcmd command with -p option to include the current directory in the ASMCMD prompt.
    #oratidbit Active Session History (ASH) sampling is available (#db12c) on Oracle ASM instances. This activity is exposed in the dynamic view V$ACTIVE_SESSION_HISTORY.
    #oratidbit #db12cR2 Case-insensitive data(base) support available through collation. Can be declared on a schema, table or column level.
    #oratidbit #db12cR2 The AL32UTF8 character set is the default for the database character set in Oracle Database installs and in the Database Configuration Assistant (DBCA). In earlier versions, the default database character set was based on the operating system locale setting.
    #oratidbit #db12cR1 OPTIMIZER_ADAPTIVE_FEATURES functions are replaced by two new parameters in #db12cR2 OPTIMIZER_ADAPTIVE_PLANS (default TRUE), and OPTIMIZER_ADAPTIVE_STATISTICS (default FALSE).
    #oratidbit before installing #DB12cR2 Grid Infrastructure or Database, simplify OS configuration by installing oracle-database-server-12cR2-preinstall RPM.
    #oratidbit Starting with Oracle Database 12c Release 1 (12.1.0.2), the roothas.sh script replaces the roothas.pl script in the Oracle Grid Infrastructure home.
    #oratidbit To enable or disable a particular database feature for an Oracle home, shut down the database and use the “chopt” tool.
    #oratidbit #db12cR2 New function ORA_MAX_NAME_LEN_SUPPORTED can be used to check the maximum length of identifiers allowed in the database. In #DB12cR2, if COMPATIBLE parameter is set to 12.1.0 or lower, the limit is 30 bytes.
    #oratidbit The pl/sql package DBMS_DB_VERSION provides the Oracle version numbers and other information useful for simple conditional compilation based on version and release.
    #oratidbit “In a future PL/SQL release, to accommodate emerging SQL standards, VARCHAR might become a separate data type, no longer synonymous with VARCHAR2.” — A note from PL/SQL Language Reference Document.
    #oratidbit PL/SQL data types PLS_INTEGER, BINARY_FLOAT and BINARY_DOUBLE use hardware arithmetic and are faster than NUMBER data type (uses library arithmetic).
    #oratidbit PL/SQL package DBMS_PARALLEL_EXECUTE can be used to implement DML parallelism in PL/SQL manually; you can execute a SQL or PL/SQL statement in parallel by taking the data to be processed and breaking it up into multiple smaller chunks.
    #oratidbit #db12cR2 #sqlplus New SET LOBPREFETCH to define the amount of LOB data (in bytes) to prefetch from database at one time. Default is 0, meaning prefetching is off. Maximum value is 2GB.
    #oratidbit #db12cR2 #sqlplus New SET ROWPREFETCH to define the number of rows to prefetch from database at one time. Default is 1. The amount of data contained in the prefetched rows should not exceed 2GB.

  • Oracle Tidbits – January 2017 #oratidbit

    “Oracle *daily* TidBits” (#oratidbit) published on Facebook, Twitter and Google+ during weekdays in January 2017. 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 #DB12cR2 In 12.2, Local temporary tablespace can be created using LOCAL TEMPORARY TABLESPACE clause of CREATE TABLESPACE. In RAC environment, local temporary tablespaces store a separate, nonshared temp files for each database instance, which can improve I/O performance. A local temporary tablespace must be a BIGFILE tablespace.
    #oratidbit A non-partitioned table in Oracle #DB12cR2 can be converted to a partitioned table by using the MODIFY clause of ALTER TABLE. MODIFY PARTITION clause specifies the partition properties.
    #oratidbit Starting with #Exadata release 12.1.2.2.0, Oracle Exadata database nodes, Oracle Exadata Virtual Server nodes (dom0), and Oracle Exadata Virtual Machines (domU) can be updated, rolled back, and backed up using patchmgr. Using patchmgr enables you to run a single command to update multiple nodes; you do not need to run dbnodeupdate.sh separately on each node. patchmgr can update the nodes in a rolling or non-rolling fashion.
    #oratidbit #db12cR2 The OPTIMIZER_ADAPTIVE_FEATURES initialization parameter is desupported in Oracle Database 12c Release 2 (12.2.0.1).
    #oratidbit #db12cR2 The ON STATEMENT refresh mode refreshes materialized views every time a DML operation is performed on any base table, without the need to commit the transaction. This mode does not require you to maintain materialized view logs on the base tables.
    #oratidbit In #db12c the SIMILAR value for the CURSOR_SHARING initialization parameter is deprecated. Use FORCE instead.
    #oratidbit #db12cR2 New initialization parameter DATA_GUARD_SYNC_LATENCY, enables you to define the maximum amount of time (in seconds) that the primary database may wait before disconnecting subsequent standby destinations after at least one synchronous standby has acknowledged receipt of the redo.
    #oratidbit #db12cR2 Using initialization parameter ENABLED_PDBS_ON_STANDBY specify a subset of pluggable databases (PDBs) for replication on a physical standby of a multitenant container database (CDB). In 12.1, you had to replicate either all PDBs or none.
    #oratidbit #db12cR2 Password file changes done on the primary database are now automatically propagated to standby databases. The only exception to this is far sync instances. Updated password files must still be manually copied to far sync instances because far sync instances receive redo, but do not apply it.
    #oratidbit #db12cR2 DBMS_JOB package is deprecated, and may be desupported in a future release. Move to DBMS_SCHEDULER.
    #oratidbit #db12cR2 By default, permissions to read and write to the System Global Area (SGA) are limited to the Oracle software installation owner only. In previous releases, both the Oracle installation owner account and members of the OSDBA group had access to shared memory.
    #oratidbit #db12cR2 Initialization parameter ALLOW_GROUP_ACCESS_TO_SGA determines if the Oracle Database installation owner account is the only user that can read and write to the database System Global Area (SGA), or if members of the OSDBA group can read the SGA. In Oracle Database 12c Release 2 (12.2), the default value for this parameter is FALSE.
    #oratidbit #db12cR2 Parallel Upgrade Utility using command-line batch script catupgrd.sql is no longer distributed with 12.2. Run the parallel upgrade utility by using command dbupgrade on Linux/Unix and dbupgrade.com for Windows.
    #oratidbit Oracle #DB12c Feature: In-database archiving is enabled by using the attribute ROW ARCHIVAL in the CREATE TABLE or ALTER TABLE statements. Invisible column ORA_ARCHIVE_STATE is added to the table with default value 0 (not archived).
    #oratidbit #db12cR2 The SYSRAC administrative privilege is used by the Clusterware agent in its connection to the database on behalf of Oracle RAC utilities, such as SRVCTL. The SYSRAC privilege provides only the minimal privileges necessary for performing day-to-day Oracle RAC operations.
    #oratidbit #db12cR2 SQL*Plus supports command history; SET HISTORY enables users to run, edit, or delete previously used SQL*Plus, SQL, or PL/SQL commands from the history list in the current session.
    #oratidbit #db12cR2 The SET MARKUP SQL*Plus command supports the display of data in CSV format. Produce output in HTML or CSV format.
    #oratidbit #db12cR2 The SET FEEDBACK ONLY SQL*Plus command returns just the number of rows returned by the query without displaying the query result.
    #oratidbit #db12cR2 CDB root and individual PDBs store, view, and manage AWR data. You can take an AWR snapshot at a CDB-level (root), as well as at a PDB-level (individual PDBs). In 12cR1, AWR snapshots are at CDB level (root) and included information from CDB and all PDBs.
    #oratidbit #db12cR2 When you take AWR snapshot at CDB level, snapshot data is stored in SYSAUX tablespace of CDB. The PDB-level snapshot data is stored in the SYSAUX tablespace of a PDB.