OracleNotes

Category: TidBits

  • Oracle Tidbits – October 2015 #oratidbit

    “Oracle *daily* TidBits” (#oratidbit) published at https://www.facebook.com/oraclenotes on weekdays in October 2015. There were no tidbits during the week of OOW15. 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 ARSn (ASM Recovery Slave) processes (new in 12c) are spawned by ASM RBAL process to recover aborted ASM transactional operations. ARSn runs only on ASM instance.
    #oratidbit TMON process is new in #DB12c for Oracle Data Guard. TMON monitors the redo transport processes for hangs and death.
    #oratidbit CTWR (change tracking writer) process tracks changed data blocks as part of the Recovery Manager block change tracking feature.
    #oratidbit ASM Disk Scrubbing Master Process SCRB is new in #DB12c. SCRB runs in an Oracle ASM instance and coordinates Oracle ASM disk scrubbing operations. Related processes are ASM Disk Scrubbing Slave Check Process (SCCn), ASM Disk Scrubbing Slave Repair Process (SCRn), ASM Disk Scrubbing Slave Verify Process (SCVN)
    #oratidbit SGA Allocator process SAnn is new in #DB12c. A small fraction of SGA is allocated during instance startup. The SAnn process allocates the rest of SGA in small chunks. The process exits upon completion of SGA allocation.
    #oratidbit ASM Recovery Slave Process ARSn is new in #DB12c. The ASM RBAL background process coordinates and spawns one or more of these slave processes to recover aborted ASM transactional operations. These processes run only in the Oracle ASM instance.
    #oratidbit Manageability Monitor Process MMON in #DB12c collects statistics for the Automatic Workload Repository. MMON is started when the database instance starts.
    #oratidbit Rolling Migration Monitor Process RMON is new in #DB12c. RMON manages the rolling migration procedure for an Oracle ASM cluster (The RMON process is spawned on demand to run the protocol for transitioning an ASM cluster in and out of rolling migration mode)
    #oratidbit RAT Masking Slave Process is new in #DB12c. This background process is used with Data Masking and Real Application Testing.
    #oratidbit Log Writer Slave process LGn is new in #DB12c. On multiprocessor systems, LGWR creates slave processes to improve the performance of writing to the redo log. LGWR slaves are not used when there is a SYNC standby destination.
    #oratidbit Listener Registration Process LREG is new in #DB12c. LREG notifies the listeners about instances, services, handlers, and endpoint. In earlier releases, PMON had this responsibility.
    #oratidbit Space Management Coordinator Process SMCO in #DB12c coordinates the execution of various space management related tasks, such as proactive space allocation and space reclamation. SMCO is started when the database instance starts.
    #oratidbit Using the “crsctl replace votedisk” command, you can move a given set of RAC voting disks from one Oracle ASM disk group into another, or onto a certified file system.

  • Oracle Tidbits – August 2015 #oratidbit

    “Oracle *daily* TidBits” (#oratidbit) published at https://www.facebook.com/oraclenotes 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.