Database Reference
In-Depth Information
RONDB_
RONDB_
GRD
recove
LGW
SMO
DBW
DBW
SMO
LMS
Fast Recovery Area (FRA) :
FRA)
2
2
1
2
1
1
1
2
1
2
Online
Redo logs
1
2
Archive
logs
Figure 8-5.
RAC database FRA settings
Crash Recovery
In the event of a RAC database having an all-instances failure, the instance that comes up first will perform the crash
recovery on behalf of the database. As already explained in the section 'Shared Location for Redo and Archive Logs,'
ensure that all instances are able to access each others' redo logs in order to perform the recovery operations.
Parallel Recovery
In this section, we will explain and provide some guidelines to enhance the recovery duration, key parameters, and
other settings that reflect improving the recovery time significantly to ensure quick database or instance accessibility.
The duration required for an instance or crash recovery plays a pretty important role in instance and database
accessibility to the end user for general usage. It is indeed essential to consider appropriate actions and steps to
enhance the recovery time.
On a multiple CPU resource-based node, Oracle automatically sets the optimal degree of parallelism and does
the instance recovery in parallel to run the recovery operations. You can also make use of the
RECOVERY_PARALLISM
and
PARALLEL_MIN_SERVERS
initialization parameters to enable parallelism. When the
RECOVERY_PARALLISM
parameter value is set to 2 or higher but can't be higher than the
PARALLEL_MAX_SERVER
value, Oracle automatically
sets the degree of parallelism for instance/crash recovery operations. Set the parameter
RECOVERY_PARALLELISM
value
either to 0 or 1 on a multi-CPU-based server to disable parallel recovery option.
Ensure that your platform supports async I/O and is enabled. It can also be enabled by setting the DISK_
ASYNCH_IO init parameter value to TRUE. The async I/O plays a key role in improving instance recovery during the
first phase (first-pass log read) of recovery.
Another way of improving the instance recovery time is to have an adequate DEFAULT CACHE size of the DB
BUFFER CACHE SIZE, as instance recovery utilizes about 50% of the DEFAULT CACHE size from the actual default
