We all know adaptive query feature introduced in Oracle Database Release 1 is a problem. Recently I had the opportunity to review few 12cR1 databases and found that to alleviate the performance problems, the DBA set parameter OPTIMIZER_FEATURES_ENABLE=11.2.0.4 in Oracle Database 12c Release 1 (12.1.0.2). This observation is the catalyst for the blog “Adaptive Query Patches in Oracle Database 12c Release 1” on my Company Blog. Oracle Support team provided options to turn off the new feature (OPTIMIZER_ADAPTIVE_FEATURES=FALSE) or to fix the issues with a Proactive Bundle Patch or with a one-off patch. Please read the blog to find out the options DBA have to fix the adaptive query optimization problem in Oracle Database 12c Release 1.
Oracle Tidbits – November 2017 #oratidbit
“Oracle *daily* TidBits” (#oratidbit) published on Facebook, Twitter, and Google+ during weekdays in November 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 #orcldb The ALTER DATABASE LINK statement is intended only to update fixed-user database links with the current passwords of connection and authentication users. |
| #oratidbit #orcldb Oracle database issues implicit COMMIT 1) before any syntactically valid DDL statement 2) after any DDL statement that completes without an error. |
| #oratidbit #orcldb Database virtual columns supported only in relational heap tables. Virtual columns are not supported for index-organized, external, object, cluster, or temporary tables. |
| #oratidbit When flashback is enabled or when there are guaranteed restore points, the background process RVWR writes flashback data to flashback database logs in the fast recovery area. |
| #oratidbit If neither AS SYSBACKUP nor AS SYSDBA is specified in the RMAN connection string, then the default used is AS SYSDBA. |
| #oratidbit You cannot use Flashback Database to undo a shrink data file operation. You may take the shrunken file offline, flash back the rest of the database, and then later restore and recover the shrunken data file. |
| #oratidbit During block media recovery, the affected data file is online and usable. Only the blocks actually being recovered are unavailable during the recovery. |
| #oratidbit The V$FLASHBACK_DATABASE_STAT view shows the bytes of flashback data logged by the database. The FLASHBACK_DATA and REDO_DATA columns describe bytes of flashback data and redo data written respectively during the time interval. |
| #oratidbit #orcldb The FLASHBACK TABLE is executed in a single transaction, regardless of the number of tables specified in the Flashback list. If the operation fails on any table, then the entire statement fails. |
| #oratidbit #orcldb To FLASHBACK DATABASE the database must run in ARCHIVELOG mode. |
| #oratidbit #orcldb When using DROP PLUGGABLE DATABASE statement to drop a PDB, you must be connected to the ROOT PDB as SYSDBA or SYSOPER. |
| #oratidbit #db12cR2 Use the new -T option for the parallel upgrade utility (catctl.pl) to set user tablespaces automatically to READ-ONLY during an upgrade. After the upgrade, the tablespaces are changed back automatically to READ/WRITE. |
| #oratidbit #db12cR2 Use the new -R option for the parallel upgrade utility (catctl.pl) to resume the upgrade at the point of failure, so that only the missing upgrade phases are rerun – Automatic Resume After Failed Upgrades feature. |
| #oratidbit #db12cR2 The Parallel Upgrade Utility (catctl.pl) parameter -N controls the number of parallel SQL processes to use when upgrading databases. |
| #oratidbit #oracleoem All operations performed by Enterprise Manager users such as creating users, granting privileges, starting a remote job, can be recorded and audited. Enable the Audit Framework using “emcli enable_audit”. |
| #oratidbit #oracleoem My Oracle Support connectivity in OEM Cloud Control enables you to view service request information, obtain patch recommendations, and download plug-ins and other entities to the Software Library, all from the Cloud Control Console. |
| #oratidbit #oracleoem Always-On Monitoring is a self-contained application that is supplied with the Enterprise Manager software distribution (sysman/ems directory) and is also available via the Self-Update function in Enterprise Manager. |
| #oratidbit Oracle Linux provides the yum utility to install or upgrade RPM packages. Yum also installs or upgrades any package dependencies. |
| #oratidbit #db12cr2 Oracle Diagnostic Pack (AWR/ADDM) can be used on an Oracle Active Data Guard standby database that is open read-only. |
| #oratidbit An Oracle Data Guard far sync instance is a remote Oracle Data Guard destination that accepts redo from the primary database and then ships that redo to other members of the Oracle Data Guard configuration. |
| #oratidbit #db12cR2 Init parameter PDB_OS_CREDENTIAL can be used to ensure that operating system interactions are performed as a less powerful user and provide the ability to protect data belonging to one PDB from being accessed by users connected to another PDB. |