Databases Reference
In-Depth Information
Solution
Set up a large pool memory area on your database. If you are using Oracle Database 10g or newer, then consider using
automatic shared memory management (ASMM) to have Oracle automatically allocate memory to the large pool.
If you're not comfortable with using ASMM, then you can manually set the initialization parameter
large_pool_size
.
If you want to manually set the large pool size, here is Oracle's recommended formula for sizing it:
large_pool_size = num_of_allocated_channels * (16 MB + (4 * size_of_tape_buffer ))
How It Works
If you have enabled the use of I/O slaves, we recommend that you set up a large pool memory area. When using I/O
slaves for synchronous I/O, RMAN will use memory in the large pool if it is available. If a large pool memory is not
available, RMAN will allocate memory from the shared pool. If RMAN cannot allocate enough memory, it will acquire
memory from the PGA and write an
ORA-04031
message to your alert.log file.
Using I/O slaves can improve performance when performing I/O to synchronous devices such as tape drives.
You enable tape I/O slaves by setting the
backup_tape_io_slaves
parameter to TRUE. This causes an I/O server
processes (slaves) to be assigned to each tape channel being used.
■
see Mos note 73354.1 for details on how the use of i/o slaves can affect rMan's use of memory buffers for
backup and recovery operations.
Tip
If you are working with an OS that doesn't support asynchronous I/O, then you can enable disk I/O slaves via
the
dbwr_io_slaves
parameter. If you set this parameter to a nonzero value, RMAN will use four server processes to
perform backup and recovery operations.
■
You can display the component name and associated memory area (shared, large, Java, or streams pool) of
structures using the sga by querying the V$sgasTaT view. For example:
Tip
SQL> select pool, name, bytes from v$sgastat;
Managing Files in an ASM Environment
Problem
You're using Oracle's automatic storage management (ASM) to manage your disks. You want to view the data files and
RMAN backup pieces that are stored on ASM disk groups.
Solution
Use the ASMCMD utility to manage RMAN files and database files when using ASM-managed disks. Ensure that your
ORACLE_SID and ORACLE_HOME environment variables are set properly for your ASM instance. Type
asmcmd -p
from
the operating system to invoke the utility:
C:\> asmcmd -p
