Comments on: Block Change Tracking setup and measurement http://dboptimizer.com/2011/05/31/block-change-tracking-setup-and-measurement/ database performance, SQL tuning and data visualizatoin Sat, 03 Mar 2018 05:02:37 +0000 hourly 1 http://wordpress.org/?v=3.6 By: Kyle Hailey http://dboptimizer.com/2011/05/31/block-change-tracking-setup-and-measurement/#comment-866 Kyle Hailey Thu, 17 Nov 2011 23:54:51 +0000 http://dboptimizer.com/?p=998#comment-866 Another good piece of information thanks to Francisco Sanchez, is preparing for the size of the BCT file:
Minimum size is 11MB, with increments of 10MB as needed.

The following query can be used to calculate the maximum size the BCT from the number of files in the database, for a non RAC case:
SELECT((
(SELECT SUM(ceil(bytes /(7686 * 1024 * 1024))) * 8 bitmap_ext
FROM v$datafile) +
(SELECT ceil(VALUE / 252) file_descr_ext
FROM v$parameter
WHERE name = ‘db_files’) + 1) *
32 + 1088) / 1024 bct_file_size_mb
FROM dual;

However if the result is less than 11 MB, then the size will be 11 MB.

]]> By: Kyle Hailey http://dboptimizer.com/2011/05/31/block-change-tracking-setup-and-measurement/#comment-398 Kyle Hailey Fri, 17 Jun 2011 20:30:58 +0000 http://dboptimizer.com/?p=998#comment-398 In some cases enabling BCT could run into the old ORA-4031

SQL> alter database enable block change tracking using file ‘/oracle/block_change.dbf’;
alter database enable block change tracking using file ‘/oracle/block_change.dbf’
*
ERROR at line 1:
ORA-19760: error starting change tracking

from init.ora

Fri Jun 17 17:13:01 2011
alter database enable block change tracking using file ‘/oracle/block_change.dbf’
Fri Jun 17 17:13:01 2011
Block change tracking file is current.
Starting background process CTWR
CTWR started with pid=276, OS id=2537
Fri Jun 17 17:13:02 2011
Errors in file /oracle/xxx_ctwr_2537.trc:
ORA-04031: unable to allocate 1826720 bytes of shared memory (“shared pool”,”unknown object”,”sga heap(1,0)”,”CTWR dba buffer”)
Block change tracking service stopping.
Fri Jun 17 17:13:02 2011
Stopping background process CTWR
ORA-19760 signalled during: alter database enable block change tracking using file ‘/oracle/block_change.dbf’…
Deleted file /oracle/block_change.dbf

and the error persists even after flushing the shared pool and in many cases bouncing the database may not be an option.

Two options are to increase large pool or reduce the BCT buffer

1) example: alter system set large_pool_size = 100M;
2) tweak hidden parameter _bct_public_dba_buffer_size but only as a last resort

]]> By: Log Buffer #223, A Carnival of the Vanities for DBAs | The Pythian Blog http://dboptimizer.com/2011/05/31/block-change-tracking-setup-and-measurement/#comment-356 Log Buffer #223, A Carnival of the Vanities for DBAs | The Pythian Blog Fri, 03 Jun 2011 08:27:14 +0000 http://dboptimizer.com/?p=998#comment-356 [...] and were afraid to ask, check out the awesome presentation from Alex Gorbechev, the Pythian CTO, Kyle Hailey [...]

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