|
|
| |
 |
|
The UNIX buffer cache
Oracle Tips by Burleson Consulting
|
The UNIX buffer cache
Just as Oracle has data buffer caches in RAM memory, UNIX
also utilizes a RAM buffer to minimize unnecessary disk I/O.
This buffer is commonly known as the Journal File System or
JFS buffer. When Oracle data is retrieved from the Oracle
database, the data block often travels through several
layers of RAM caches (Figure 2-4).
Figure 4: Multiple UNIX RAM buffer caches
As we see in Figure 2-4, when Oracle makes a request to
fetch a data block, the Oracle data buffer is first checked
in ensure that the block is not already in the Oracle
buffer. If it is not, the UNIX JFS buffer will then be
checked for the data block. If the data block is not in the
JFS buffer, the disk array buffer is then checked. Only when
none of these three buffers contains the data block is a
physical disk read incurred. |
 |
Expert Remote DBA
BC is America's oldest and largest Remote DBA Oracle support
provider. Get real Remote DBA experts, call
BC Remote DBA today. |
 |
|
|
|
|
