EMC Backup and Recovery for Oracle 11g OLTP Enabled by EMC ...

Chapter 6: Testing and Validation
The graph below shows the response time from the CLARiiON CX4-960 for the
duration of the backup process. Here, the Swingbench load is running against the
RAC node cluster. This initiates synchronization of the clone copy on completion of
the sync, the database is put in hot backup mode. The clones are then fractured, the
database is taken out of hot backup mode, and the clones are mounted to the proxy
host. NetWorker then initiates the backup from the proxy host. The response time
remains steady except for two short periods, explained below.
Pointer 1: The first increase occurs when the clone copy is initiated.
Pointer 2: The second increase in response time occurs when the database is put
into hot backup mode. The spike occurs when the database is put into hot backup
mode because:
• Any dirty data buffers in the database buffer cache are written out to files
and the datafiles are checkpointed.
• The datafile headers are updated to the system change number (SCN),
captured when the begin backup command is issued. The SCN is not
incremented with checkpoints while a file is in hot backup mode. This lets the
recovery process understand which archive redo log files may be required to
fully recover this file from that SCN onward.
• The datablocks within the database files continue to be read and written to.
• During hot backup, an entire block is written to the redo log files the first time
the data block is changed. Subsequently, only redo vectors (changed bytes)
are written to the redo logs.
Pointer 3: When the database is taken out of hot backup mode, the datafile header
and SCN are updated.
Pointer 4: The clone copy is then mounted to the proxy node and the RMAN backup
is launched from NetWorker using the proxy host, which is a dedicated storage node.
EMC Backup and Recovery for Oracle 11g OLTP Enabled by EMC CLARiiON, EMC Data Domain, EMC NetWorker,
and Oracle Recovery Manager using NFS Proven Solution Guide
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