Tales From A Lazy Fat DBA

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Archive for September, 2022

Are you looking for a method to stop automatic SQL quarantine without disabling the entire SQL Quarantine feature ? Welcome to Oracle 21c …

Posted by FatDBA on September 23, 2022

Hi All,

Recently I was working on a 21c database for a POC where at one point I want to disable automatic creation of SQL Quarantine, but without disabling the entire statement Quarantine feature. This 21.3.0.0.0 Database had got the resource manager enabled, and one of the SQL was taking long time to complete, longer than the allowed directive limits on IO & CPU TIME, and as expected the SQL was killed with message “ORA-00040: active time limit exceeded – call aborted” and the SQL plan was quarantined. I wanted to stop or disable the auto creation of SQL Quarantines for the SQL in question, after RM terminates the SQL.

If you want to read more about SQL Quarantine, please click this link to my earlier post with a demo about it.

I remember in 19c there wasn’t any way to achieve that and can only regulate behavior using two of the underscore parameters _quarantine_enabled or _optimizer_quarantine_sql. Oracle 21c has introduced two two new parameters to control the behavior of SQL Quarantine, and that specially solves this issue.

First one is optimizer_capture_sql_quarantine, if set to FALSE, would disable the automatic creation of SQL Quarantine configurations after RM termination of a SQL query execution. This is FALSE by default.

The second parameter is optimizer_use_sql_quarantine, if set to FALSE would disable the use of existing SQL Quarantine configurations in a database. This parameter determines whether the optimizer considers SQL Quarantine configurations when choosing an execution plan for a SQL statement. This is TRUE by default, thereby allowing users to manually create and use SQL Quarantine configurations.

Oracle Database 21c Enterprise Edition Release 21.0.0.0.0 - Production
Version 21.3.0.0.0

-- Default Setting
SQL> show parameter OPTIMIZER_CAPTURE_SQL_QUARANTINE

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
optimizer_capture_sql_quarantine     boolean     FALSE
SQL>
SQL>

-- Default Setting
SQL> sho parameter OPTIMIZER_USE_SQL_QUARANTINE

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
optimizer_use_sql_quarantine         boolean     TRUE
SQL>
SQL>

Hope It Helped!
Prashant Dixit

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FRA full with archives ORA-38706 ORA-38708 ? Not always think of a BUG … And when that proud little DBA in me missed common sense

Posted by FatDBA on September 11, 2022

Hi All,
Some time back I was working on an 19.16 database where I’d to enable FLASHBACK on a database, but immediately kicked out with an error “ORA-38706: Cannot turn on FLASHBACK DATABASE logging. ORA-38708: not enough space for first flashback database log file”. So, I’d tried to expand the FRA size, but thought to check what there inside the FRA, it was 99.9% full with 270 archive log files occupying 99.39% of the total allocated space. So, everything was good till that point.

[oracle@fatdba ~]$ sqlplus / as sysdba

SQL*Plus: Release 19.0.0.0.0 - Production on Mon Sep 5 19:07:28 2022
Version 19.16.0.0.0

Copyright (c) 1982, 2022, Oracle.  All rights reserved.


Connected to:
Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.16.0.0.0

SQL>
SQL> show parameter db_recovery_file_dest_size

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
db_recovery_file_dest_size           big integer 251G


NAME         SPACE_LIMIT_GB SPACE_AVAILABLE_GB PERCENT_FULL
------------ -------------- ------------------ ------------
+RECO                   251         .240234375         99.9


FILE_TYPE               PERCENT_SPACE_USED PERCENT_SPACE_RECLAIMABLE NUMBER_OF_FILES     CON_ID
----------------------- ------------------ ------------------------- --------------- ----------
CONTROL FILE                             0                         0               1          0
REDO LOG                                 0                         0               0          0
ARCHIVED LOG                         99.39                         0             270          0
BACKUP PIECE                           .01                         0               2          0
IMAGE COPY                               0                         0               0          0
FLASHBACK LOG                            0                         0               0          0
FOREIGN ARCHIVED LOG                     0                         0               0          0
AUXILIARY DATAFILE COPY                  0                         0               0          0

But I thought to check space at the ASM Level. I queried v$asm_diskgroup and results were totally opposite with what I saw with V$RECOVERY_FILE_DEST and v$flash_recovery_area_usage. RECO Disk Group (FRA location) was almost 100% free and only 0.54% was consumed. Same results were there when I’d queried RECO DG via asmcmd.

-- results from v$asm_diskgroup view
Disk Group            Sector   Block   Allocation
Name                    Size    Size    Unit Size State       Type   Total Size (MB) Used Size (MB) Pct. Used
-------------------- ------- ------- ------------ ----------- ------ --------------- -------------- ---------
DATA                     512   4,096    1,048,576 CONNECTED   EXTERN         691,197        356,322     51.55
OCRVFDG                  512   4,096    4,194,304 MOUNTED     EXTERN          25,596            100       .39
RECO                     512   4,096    1,048,576 CONNECTED   EXTERN       1,048,575          5,645       .54
                                                                     --------------- --------------
Grand Total:                                                               1,765,368        362,067



ASMCMD> lsdg
State    Type    Rebal  Sector  Logical_Sector  Block       AU  Total_MB  Free_MB  Req_mir_free_MB  Usable_file_MB  Offline_disks  Voting_files  Name
MOUNTED  EXTERN  N         512             512   4096  1048576    691197   334875                0          334875              0             N  DATA/
MOUNTED  EXTERN  N         512             512   4096  4194304     25596    25496                0           25496              0             N  OCRVFDG/
MOUNTED  EXTERN  N         512             512   4096  1048576   1048575  1043233                0         1043233              0             N  RECO/
ASMCMD>

At this point I’d started thinking about some kind of a BUG in the database, I know about few FRA related bugs in earlier Oracle versions. Just before I’d tried anything else, I thought to execute dbms_backup_restore.refreshagedfiles which refreshes the view. At the same time tried kra_options event which resets v$recovery_file_dest, but no luck 😦

SQL>
SQL> alter session set events 'immediate trace name kra_options level 1';

Session altered.

SQL>  execute dbms_backup_restore.refreshagedfiles;

PL/SQL procedure successfully completed.

SQL>

And right at that point I was very sure it was happening all due to a bug and was thinking to contact Oracle support. But just before that, that proud little DBA in me thought, Am I missing something ? Any other possible areas I should have explored before connecting with OCS ?

I’d checked RMAN to see if it still has any expired archivelog details and ran ‘crosscheck archivelog all’, and it identified exactly 270 older archivelogs which were non existent. So, that proud little DBA was wrong 🙂 .. When the count was matched exactly with the v$flash_recovery_area_usage, I’d deleted all of those expired archivelogs from catalog.

-- To Crosscheck all archivelog files present in the RMAN catalog.
RMAN> crosscheck archivelog all;

using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=258 device type=DISK
validation failed for archived log
archived log file name=+RECO/FATDBA/ARCHIVELOG/2022_07_02/thread_1_seq_1.261.1109109619 RECID=1 STAMP=1109109620
validation failed for archived log
archived log file name=+RECO/FATDBA/ARCHIVELOG/2022_07_02/thread_1_seq_2.264.1109401205 RECID=2 STAMP=1109401206
validation failed for archived log
.....
........
..........
..............
validation failed for archived log
archived log file name=+RECO/FATDBA/ARCHIVELOG/2022_07_02/thread_1_seq_268.463.1114203831 RECID=268 STAMP=1114203829
validation failed for archived log
archived log file name=+RECO/FATDBA/ARCHIVELOG/2022_07_02/thread_1_seq_269.469.1114207455 RECID=269 STAMP=1114207454
validation succeeded for archived log
archived log file name=+RECO/FATDBA/ARCHIVELOG/2022_07_02/thread_1_seq_321.531.1114624193 RECID=270 STAMP=1114624193
Crosschecked 270 objects


-- Delete expired archivelog files
RMAN>
RMAN>
RMAN> delete expired archivelog all;
...
.......
270     1    270     X 31-AUG-22
        Name: +RECO/FATDBA/ARCHIVELOG/2022_07_02/thread_1_seq_268.463.1114203831 RECID=268 STAMP=1114203829
..
.......
Do you really want to delete the above objects (enter YES or NO)? YES
deleted archived log
archived log file name=+RECO/FATDBA/ARCHIVELOG/2022_07_02/thread_1_seq_1.261.1109109619 RECID=1 STAMP=1109109620
deleted archived log
archived log file name=+RECO/FATDBA/ARCHIVELOG/2022_07_02/thread_1_seq_2.264.1109401205 RECID=2 STAMP=1109401206
deleted archived log
archived log file name=+RECO/FATDBA/ARCHIVELOG/2022_07_02/thread_1_seq_3.265.1109671797 RECID=3 STAMP=1109671799
deleted archived log
archived log file name=+RECO/FATDBA/ARCHIVELOG/2022_07_02/thread_1_seq_4.266.1109955617 RECID=4 STAMP=1109955618
deleted archived log
archived log file name=+RECO/FATDBA/ARCHIVELOG/2022_07_02/thread_1_seq_5.267.1110233333 RECID=5 STAMP=1110233334
deleted archived log
archived log file name=+RECO/FATDBA/ARCHIVELOG/2022_07_02/thread_1_seq_6.268.1110485231 RECID=6 STAMP=1110485232
deleted archived log
Deleted 270 EXPIRED objects

RMAN>
RMAN>

And immediately I saw the change in FRA related dynamic views (V$RECOVERY_FILE_DEST and v$flash_recovery_area_usage) and matched the genuine utilization at the ASM level.

[oracle@fatdba ~]$ sqlplus / as sysdba

SQL*Plus: Release 19.0.0.0.0 - Production on Mon Sep 5 19:07:28 2022
Version 19.16.0.0.0

Copyright (c) 1982, 2022, Oracle.  All rights reserved.


Connected to:
Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.16.0.0.0

SQL>
SQL>
SQL> SELECT NAME,
       (SPACE_LIMIT / 1024 / 1024 / 1024) SPACE_LIMIT_GB,
         ((SPACE_LIMIT - SPACE_USED + SPACE_RECLAIMABLE) / 1024 / 1024 / 1024) AS SPACE_AVAILABLE_GB,
       ROUND((SPACE_USED - SPACE_RECLAIMABLE) / SPACE_LIMIT * 100, 1) AS PERCENT_FULL
  FROM V$RECOVERY_FILE_DEST;  

NAME         SPACE_LIMIT_GB SPACE_AVAILABLE_GB PERCENT_FULL
------------ -------------- ------------------ ------------
+RECO                   200          197.59082          1.2

SQL> select * from v$flash_recovery_area_usage;

FILE_TYPE               PERCENT_SPACE_USED PERCENT_SPACE_RECLAIMABLE NUMBER_OF_FILES     CON_ID
----------------------- ------------------ ------------------------- --------------- ----------
CONTROL FILE                           .01                         0               1          0
REDO LOG                                 0                         0               0          0
ARCHIVED LOG                           .57                         0               2          0
BACKUP PIECE                           .01                       .01               2          0
IMAGE COPY                               0                         0               0          0
FLASHBACK LOG                            0                         0               0          0
FOREIGN ARCHIVED LOG                     0                         0               0          0
AUXILIARY DATAFILE COPY                  0                         0               0          0

8 rows selected.

Hope It Helped!
Prashant Dixit

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A new 21c dynamic view securefile_shrink, and possibly a new BUG in 21.3. I guess I have identified a BUG

Posted by FatDBA on September 1, 2022

Recently I was doing a POC on Oracle 21c, and I had to shrink an LOB secure file column, and I was aware about a new dynamic view added to Oracle 21c called V$SECUREFILE_SHRINK, which is very useful to monitor securefiles shrink operations. This gives you some great details like start time, end time, status of the operation etc. I shrank one of the required securefile LOB column of a table and I was interested to see what all was captured by V$SECUREFILE_SHRINK … But It was empty!! got ‘no rows selected’, Why is that ??

Let me try to replicate the scenario and explain what I was doing that day.

-- Let me create a test scenario
-- Will create a brand new playground to test all things
[oracle@witnessalberta ~]$ !sq
sqlplus / as sysdba

SQL*Plus: Release 21.0.0.0.0 - Production on Sun Aug 28 10:50:26 2022
Version 21.3.0.0.0

Copyright (c) 1982, 2021, Oracle.  All rights reserved.


Connected to:
Oracle Database 21c Enterprise Edition Release 21.0.0.0.0 - Production
Version 21.3.0.0.0

SQL>
SQL>
SQL>
SQL> CREATE PLUGGABLE DATABASE pdb2 ADMIN USER pdb_adm IDENTIFIED BY oracle90 CREATE_FILE_DEST='/opt/oracle/oradata';

Pluggable database created.

SQL> show pdbs;

    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         2 PDB$SEED                       READ ONLY  NO
         3 ORCLPDB1                       MOUNTED
         4 PDB2                           MOUNTED
SQL> ALTER PLUGGABLE DATABASE pdb2 OPEN READ WRITE;

Pluggable database altered.

SQL>  ALTER SESSION SET CONTAINER = PDB2;

Session altered.

SQL> SHOW CON_NAME;

CON_NAME
------------------------------
PDB2

SQL>
SQL> conn fatdba/oracle90@PDB2
Connected.
SQL>
SQL>
SQL>
SQL> show user
USER is "FATDBA"
SQL>
SQL>
SQL>
SQL>

-- Created a Table with a SECUREFILE LOB 
SQL> CREATE TABLE secure_file_tab (rid  NUMBER(5), bcol BLOB) LOB (bcol) STORE AS SECUREFILE bcol_lob 
(TABLESPACE users DISABLE  STORAGE IN ROW CHUNK 8192 RETENTION MIN 3600 KEEP_DUPLICATES NOCOMPRESS DECRYPT CACHE READS); 

Table created.

SQL>

SQL>
-- Inserted some 100000 random rows into the table
insert into secure_file_tab VALUES(101, utl_raw.cast_to_raw('hello, this is the first review'));
insert into secure_file_tab VALUES(101, utl_raw.cast_to_raw('hello, this is the first review'));
insert into secure_file_tab VALUES(101, utl_raw.cast_to_raw('hello, this is the first review'));
insert into secure_file_tab VALUES(101, utl_raw.cast_to_raw('hello, this is the first review'));
insert into secure_file_tab VALUES(101, utl_raw.cast_to_raw('hello, this is the first review'));
insert into secure_file_tab VALUES(101, utl_raw.cast_to_raw('hello, this is the first review'));
...
......
........

SQL> select count(*) from secure_file_tab;

  COUNT(*)
----------
    100001

SQL>
SQL>
-- Lets check the size of the table.
SQL> select segment_name, bytes/1024 from dba_segments where segment_name='SECURE_FILE_TAB';

SEGMENT_NAME         BYTES/1024
-------------------- ----------
SECURE_FILE_TAB      4096

-- Have deleted all rows from the table
SQL> delete from secure_file_tab where RID=101;

100000 rows deleted.

SQL> COMMIT;

SQL> select count(*) from secure_file_tab;

COUNT(*)
----------
1

-- Gathered table stats
SQL> exec dbms_stats.gather_table_stats(null, 'secure_file_tab');

PL/SQL procedure successfully completed.


SQL> select segment_name, bytes/1024 from dba_segments where segment_name='SECURE_FILE_TAB';

SEGMENT_NAME         BYTES/1024
-------------------- ----------
SECURE_FILE_TAB      113



SQL> alter table secure_file_tab modify lob(bcol) (shrink space);

Table altered.

Now time to check if anything captured in the v$securefile_shrink or gv$securefile_shrink dynamic view about the securefile shrink operation.

-- Lets check if anything captured by the view
SQL> desc v$securefile_shrink
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 LOB_OBJD                                           NUMBER
 SHRINK_STATUS                                      VARCHAR2(40)
 START_TIME                                         TIMESTAMP(3) WITH TIME ZONE
 END_TIME                                           TIMESTAMP(3) WITH TIME ZONE
 BLOCKS_MOVED                                       NUMBER
 BLOCKS_FREED                                       NUMBER
 BLOCKS_ALLOCATED                                   NUMBER
 EXTENTS_ALLOCATED                                  NUMBER
 EXTENTS_FREED                                      NUMBER
 EXTENTS_SEALED                                     NUMBER
 CON_ID                                             NUMBER


SQL> select * from v$securefile_shrink;

no rows selected

SQL> select * from gv$securefile_shrink;

no rows selected

SQL>

Nothing!!! Why ? Why ? Let me try the other way (MOVE LOB) and see if that populates anything in v$securefile_shrink or gv$securefile_shrink. Repopulated the same table again with 100000 rows, deleted all rows from the table, committed changes, regathered stats and verified table size, same what we did in Test 1.

-- Changed the LOB SHRINK technique this time.
SQL> ALTER TABLE secure_file_tab MOVE LOB(BCOL) STORE AS (TABLESPACE test);

Table altered.


-- Lets check if anything captured by the view
SQL> select * from v$securefile_shrink;

no rows selected

SQL> select * from gv$securefile_shrink;

no rows selected

SQL>

Nothing!!! Why ? Why ? Let me try the with one more way (SHRINK SPACE CASCADE) again and see if that populates anything in v$securefile_shrink or gv$securefile_shrink. Repopulated the same table again with 100000 rows, deleted all rows from the table, committed changes, regathered stats and verified table size, same what we did in Test 1.

--Let me try the other way
SQL> alter table secure_file_tab MODIFY LOB(BCOL) (SHRINK SPACE CASCADE);

Table altered.

-- Lets check if anything captured by the view
SQL> select * from v$securefile_shrink;

no rows selected

SQL> select * from gv$securefile_shrink;

no rows selected

SQL>

Nothing!!! Why ? Why ? This is super strange now. Then finally, I decided to check with Oracle support and asked them to try at their end in 21c and from their end also it was getting populated. I guess I have identified a BUG in 21.3.0.0.0!! 🙂 🙂 Currently the case is with development team and they are taking a look on this buggy behavior on Oracle 21.5 on Red Hat Linux 7 x86_64 … Let’s see how it goes from here, will post the solution or the cause behind this ill behavior soon.

Hope It Helped!
Prashant Dixit

Posted in Advanced, troubleshooting | Tagged: , , , , | Leave a Comment »

 
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