Oracle Tidbits – August 2015 #oratidbit

Oracle *daily* TidBits” (#oratidbit) published at on weekdays in August 2015. 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…

Date TidBit
3-Aug #oratidbit In #DB12c, you can use the REPLACE clause in ALTER DISKGROUP statement instead of DROP and ADD. The single replace operation is more efficient than dropping and adding disks.
4-Aug #oratidbit Oracle ASM disk scrubbing checks logical data corruptions and repairs the corruptions automatically in normal and high redundancy disks groups. The scrubbing process is visible in fields of the V$ASM_OPERATION view.
5-Aug #oratidbit ASMCMD commands spbackup, spcopy, or spmove can be used to back up, copy, or move an Oracle ASM SPFILE.
11-Aug #oratidbit The ALTER DATABASE FORCE LOGGING statement may take long time to complete, because it waits for all NOLOGGING direct write I/O to finish.
10-Aug #oratidbit the ASMCMD pwcopy command can be used to copy an Oracle ASM or database instance password file to another location.
12-Aug #oratidbit Oracle Data Guard far sync instance is a remote Oracle Data Guard destination that accepts redo from the primary database and then ships that redo to other members of the Oracle Data Guard configuration.
13-Aug #oratidbit LOG_ARCHIVE_DEST_n parameter can include the COMPRESS attribute to ship redo logs to standby database in compressed form. Redo transport compression can significantly improve redo transport performance on network links with low bandwidth and high latency. Requires Oracle Advanced Compression option.
14-Aug #oratidbit when primary-standby role transition occurs, DB_ROLE_CHANGE system event is signalled, which can be used to fire a trigger that performs a set of actions whenever a role transition occurs.
17-Aug #oratidbit ANONYMOUS database user account allows HTTP access to Oracle XML DB. It is used in place of the APEX_PUBLIC_USER account when the Embedded PL/SQL Gateway (EPG) is installed in the database.
18-Aug #oratidbit AUDSYS is an internal database user in #DB12c used by the unified audit feature to store unified audit trail records.
19-Aug #oratidbit ASMSNMP account created in ASM instance is used by Oracle Enterprise Manager to monitor ASM instances to retrieve data from ASM-related data dictionary views. The ASMSNMP account status is set to OPEN upon instance creation, and it is granted the SYSDBA administrative privilege.
20-Aug #oratidbit X$NULL is an internal account that represents the absence of database user in a session and the actual session user is an application user supported by Oracle Real Application Security. XS$NULL has no privileges and does not own any database object. No one can authenticate as XS$NULL, nor can authentication credentials ever be assigned to XS$NULL.
21-Aug #oratidbit DBA_USERS_WITH_DEFPWD view displays users in the database (created at DB creation time) that are still using their default passwords.
24-Aug #oratidbit Set STATISTICS_LEVEL initialization parameter to TYPICAL (default) or ALL to enable statistics gathering by AWR. Setting STATISTICS_LEVEL to BASIC disables many database features, including AWR.
25-Aug #oratidbit DB time is measured cumulatively from when the instance started. Because DB time combines times from all non-idle user sessions, DB time can exceed the time elapsed since the instance started.
26-Aug #oratidbit The Active Session History (ASH) statistics are samples of session activity in the database. The database samples active sessions every second and stores them in a circular buffer in the System Global Area (SGA).
27-Aug #oratidbit CONTROL_MANAGEMENT_PACK_ACCESS initialization parameter must be DIAGNOSTIC+TUNING (default) or DIAGNOSTIC to enable ADDM (Automatic Database Diagnostic Monitor).
28-Aug #oratidbit ADDM analysis is performed after each AWR snapshot (every hour by default), and the results are saved in the database. OEM is an easy interface to access ADDM and AWR reports.
31-Aug #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, that is, the moment that the user tries to view the data.

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