Daily Archives: February 27, 2016

12c, Administration, Performance

Oracle 12c – Use Flash Cache

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The Database Smart Flash Cache allows an instance to access multiple flash devices without requiring a volume manager.  This feature only works on Solaris and Linux OS.

 

Enabling Smart Flash Cache is a benefit if:

  1. Buffer Pool Advisor of AWR or STATSPACK says to double size of buffer cache.
  2. DB FILE SEQUENTIAL READ is top wait event.
  3. System has spare CPU cycles.

 

Two initialization parameters used to configure Database Smart Flash Cache.

DB_FLASH_CACHE_FILE – list of Paths and files for Database Smart Flash Cache which can be ASM or OS files but must be on a flash device.  If not specified, oracle will create on startup.  Support max of 16 files.

DB_FLASH_CACHE_SIZE – Specifies size of each file, if number of sizes does not match number of files, an error will occur.  Size is specified by nG (ie 10G).  You disable FLASH device by specifying zero for size.  But this is not a dynamic change and restart is required.

 

V$FLASHFILESTAT view can determine latency and read counts for each file.

 

 

Larry Catt

OCP

12c, Administration, backup/recovery, RMAN

Oracle 12c New Feature – RMAN

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Table Level Recovery from backup – 12c now has the ability to recover a single table from an RMAN backup with the user of RECOVER TABLE option.

 

RMAN Command-Line SQL – RMAN utility now allows for the execution of SQL commands against target database without using SQL key word.   RMAN also now support the SQLPLUS DESCRIBE command for tables and views.

 

Active Database Duplication – RMAN supports the ability to clone a source database to an auxiliary database over the network.   Retrieving all backup sets from source database over network and allows for use of block compression during the duplication process.

 

NOOPEN option for Duplicate database creation, which allows for recovered database to not be open with resetlogs before administrative tasks can be performed.

 

duplicate target database

to newdatabase

from active database

noopen;

 

SECTION SIZE option with Image Copies – RMAN now allows you to divide data files into subsections and split upon multiple recovery channels.

 

backup

as copy

section size 500M

database;

 

Incremental Backups can include the SECTION SIZE option which allows for parallel channels to be used, thus reducing the time for backup.

 

backup

incremental level 1

section size 500m

Datafile ‘/u01/oradata/orcl/data01.dbf’;

 

SNAPSHOT with the use of BACKUP mode, 12c allows for the use of VM snapshots or storage snapshot without placing database in backup mode.   The snapshot requires 3 things for use:

  1. Database is consistent at time of snapshot.
  2. Write order is maintained for snapshot.
  3. Snapshot stores time of snapshot.

 

SNAPSHOT TIME option has become part of RECOVER command which allows for recovery from OS snapshot to a consistent point.

 

 

Larry Catt

OCP