What is RBA?
Called as Redo Byte
Address. Consuming approximate 10 bytes. It represents/identifies start of redo
record. RBA contains Log
Sequence Number (4 bytes), Block Number within Redo Log (4 bytes) and Byte number
within block (2 bytes) in started point.
There are different
types of RBA available in SGA those are following.
Low RBA
Dirty buffer contains
first redo change address called Low RBA. From x$bh we can check low RBA.
High RBA
Dirty buffer contains
last and most recent redo changes address called High RBA. From x$bh we can
check High RBA.
Checkpoint RBA
DBWR has written buffers
from checkpoint queue are pointing to checkpoint RBA while incremental
checkpoint is enabled.
This RBA copies in to control file’s checkpoint progress record. When instance
recovery occurs that
time it starts from checkpointing RBA from control file. We can check this RBA
from
x$targetrba (sometimes
from x$kccrt).
Target RBA
It is representing RBA
which DBWR want to done advance checkpoint for instance recovery (if enabled).
We can check from
x$targetrba.
On-disk RBA
That RBA which was
flushed in to online Redo Log File on disk. This RBA recorded in to control
file record
section. We can check from x$kcccp
for on-disk RBA (sometimes from x$targetrba).
