block change tracking buffer space !
From: Nitin Saxena <ntnsxn7_at_gmail.com>
Date: Mon, 12 Mar 2018 17:48:08 -0700
Message-ID: <CAM+YwA_usUdgs2QUM_b4xHweqJUX4ugOUWWYdovaPUpr8mcHpg_at_mail.gmail.com>
Hello Everyone,
Date: Mon, 12 Mar 2018 17:48:08 -0700
Message-ID: <CAM+YwA_usUdgs2QUM_b4xHweqJUX4ugOUWWYdovaPUpr8mcHpg_at_mail.gmail.com>
Hello Everyone,
I am facing lot of concurrency wait events due to "block change tracking buffer space" when rman L0 backup is run. I see that database gets overwhelmed with concurrency due to less space for CTWR buffer as shown in event. I see following problem area . Any recommendations if we should bump "_bct_public_dba_buffer_size" to higher value ?
NAME
VALUE DESCRIPTION --------------------------------------------- ------------------------------ ------------------------------ -------------------------buffers,
_bct_public_dba_buffer_size
0 total size of all public change tracking dba
in bytes
NAME
VALUE DESCRIPTION --------------------------------------------- ------------------------------ ------------------------------ -------------------------allocations,
_bct_buffer_allocation_max
104857600 maximum size of all change tracking buffer
in bytes
SQL> select dba_buffer_count_public*dba_entry_count_public*dba_entry_size from X$KRCSTAT;
DBA_BUFFER_COUNT_PUBLIC*DBA_ENTRY_COUNT_PUBLIC*DBA_ENTRY_SIZE
25276400
SQL> SELECT * FROM v$sgastat WHERE name like 'CTWR%';
POOL NAME BYTES ------------ -------------------------- ---------- large pool CTWR dba buffer 11386880
snippet from ash and dash is as follows:
%This SECONDS WAIT_CHAIN
------ ---------- ------------------------------ ------------------------------------------------------------ ------------------------------------------------------------ ------------------------------------------------------------ ------------------------------------------------------------ ------------------------------ 12% 14650 -> 1vyayutd1117p:buffer busy waits -> 1vyayutd1117p:blockchange tracking buffer space
-- Cheers Nitin -- http://www.freelists.org/webpage/oracle-lReceived on Tue Mar 13 2018 - 01:48:08 CET