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Archive for January, 2011

Giving Oracle a Checkup

Posted by sdefilip on January 27, 2011

ORACLE 11g HEALTH CHECK MONITOR

The Oracle Health Check Monitor (HM) facility is new with Oracle 11.1 database.  It can run diagnostic checks that detect:

>   file corruptions – reports failures if these files are inaccessible, corrupt or inconsistent. If the database is in mount or open mode, this check examines the log files and data files listed in the control file. If the database is in NOMOUNT mode, only the control file is checked.

>   physical and logical block corruptions – detects disk image block corruptions such as checksum failures, head/tail mismatch, and logical inconsistencies within the block. Most corruptions can be repaired using Block Media Recovery. Corrupted block information is also captured in the V$DATABASE_BLOCK_CORRUPTION view. This check does not detect inter-block or inter-segment corruption.

> undo and redo corruptions –

For redo, HM scans the contents of the redo log for accessibility and corruption, as well as the archive logs, if available. The Redo Integrity Check reports failures such as archive log or redo corruption.

For undo, HM finds logical undo corruptions. After locating an undo corruption, this check uses PMON and SMON to try to recover the corrupted transaction. If this recovery fails, then Health Monitor stores information about the corruption in V$CORRUPT_XID_LIST. Most undo corruptions can be resolved by forcing a commit.

>   transaction integrity check – identical to the Undo Segment Integrity Check except that it checks only one

specific transaction

>  data dictionary corruptions – examines the integrity of core dictionary objects, such as tab$ and col$. It  performs the following operations:

    • Verifies the contents of dictionary entries for each dictionary object.
    • Performs a cross-row level check, which verifies that logical constraints on rows in the dictionary are enforced.
    • Performs an object relationship check, which verifies that parent-child relationships between dictionary objects are enforced.

The Dictionary Integrity Check operates on the following dictionary objects:

tab$, clu$, fet$, uet$, seg$, undo$, ts$, file$, obj$, ind$, icol$, col$, user$, con$, cdef$, ccol$, bootstrap$, objauth$, ugroup$, tsq$, syn$, view$, typed_view$, superobj$, seq$, lob$, coltype$, subcoltype$, ntab$, refcon$, opqtype$, dependency$, access$, viewcon$, icoldep$, dual$, sysauth$, objpriv$, defrole$, and ecol$.

Each of the above checks can be used with parameters that provide specific subcategories of information.

Run HM Checker Manually

The Oracle Health Monitor (HM) can be run using the following syntax manually:

BEGIN

DBMS_HM.RUN_CHECK(‘type of check’, ‘name of HM check run’);

END;

Example:

SQL>
BEGIN

DBMS_HM.RUN_CHECK(‘Data Block Integrity Check’, ‘db_blk_integ_run’);

END;
SQL> /

The types of checks that can be obtained in this manner (in place of ‘type of check’ above) are:

HM Test Check
DB Structure Integrity Check
CF Block Integrity Check
Data Block Integrity Check
Redo Integrity Check
Logical Block Check
Transaction Integrity Check
Undo Segment Integrity Check
No Mount CF Check
Mount CF Check
CF Member Check
All Datafiles Check
Single Datafile Check
Tablespace Check Check
Log Group Check
Log Group Member Check
Archived Log Check
Redo Revalidation Check
IO Revalidation Check
Block IO Revalidation Check
Txn Revalidation Check
Failure Simulation Check
Dictionary Integrity Check
ASM Mount Check
ASM Allocation Check
ASM Disk Visibility Check
ASM File Busy Check

Most health checks accept input parameters. You can view parameter names and descriptions with the V$HM_CHECK_PARAM view. Some parameters are mandatory while others are optional. If optional parameters are omitted, defaults are used. The following query displays parameter information for all health checks:

SELECT c.name check_name, p.name parameter_name, p.type,

p.default_value, p.description

FROM v$hm_check_param p, v$hm_check c

WHERE p.check_id = c.id and c.internal_check = ‘N’

ORDER BY c.name;

Input parameters are passed in the input_params argument as name/value pairs separated by semicolons (;). The following example illustrates how to pass the transaction ID as a parameter to the Transaction Integrity Check:

BEGIN

DBMS_HM.RUN_CHECK (

check_name   => ‘Transaction Integrity Check’,

run_name     => ‘my_run’,

input_params => ‘TXN_ID=7.33.2’);

END;

Running HM Checker using Enterprise Manager:

1.      On the Database Home page, in the Related Links section, click Advisor Central.

2.      Click Checkers to view the Checkers subpage.

3.      In the Checkers section, click the checker you want to run.

4.      Enter values for input parameters or, for optional parameters, leave them blank to accept the defaults.

5.      Click Run, confirm your parameters, and click Run again.

Viewing HM Checker Reports

You can now view a report of a checker execution. The report contains findings, recommendations, and other information. You can view reports using Enterprise Manager, the ADRCI utility, or the DBMS_HM PL/SQL package. The following table indicates the report formats available with each viewing method.

Report Viewing Method Report Formats Available
Enterprise Manager HTML
DBMS_HM PL/SQL package HTML, XML, and text
ADRCI utility XML

To view run findings using Enterprise Manager

  1. Access the Database Home page.
  2. In the Related Links section, click Advisor Central.
  3. Click Checkers to view the Checkers subpage.
  4. Click the run name for the checker run that you want to view.

The Run Detail page appears, showing the findings for that checker run.

  1. Click Runs to display the Runs subpage.

Enterprise Manager displays more information about the checker run.

  1. Click View Report to view the report for the checker run.

The report is displayed in a new browser window.

Viewing Reports Using DBMS_HM

You can view Health Monitor checker reports with the DBMS_HM package function GET_RUN_REPORT. This function enables you to request HTML, XML, or text formatting. The default format is text, as shown in the following SQL*Plus example:

SET LONG 100000

SET LONGCHUNKSIZE 1000

SET PAGESIZE 1000

SET LINESIZE 512

SELECT DBMS_HM.GET_RUN_REPORT(‘HM_RUN_1061’) FROM DUAL;

DBMS_HM.GET_RUN_REPORT(‘HM_RUN_1061’)

———————————————————————–

Run Name                     : HM_RUN_1061

Run Id                       : 1061

Check Name                   : Data Block Integrity Check

Mode                         : REACTIVE

Status                       : COMPLETED

Start Time                   : 2011-01-12 22:11:02.032292 -07:00

End Time                     : 2011-01-12 22:11:20.835135 -07:00

Error Encountered            : 0

Source Incident Id           : 7418

Number of Incidents Created  : 0

Input Paramters for the Run

BLC_DF_NUM=1

BLC_BL_NUM=64349

Run Findings And Recommendations

Finding

Finding Name  : Media Block Corruption

Finding ID    : 1065

Type          : FAILURE

Status        : OPEN

Priority      : HIGH

Message       : Block 64349 in datafile 1:

‘/ade/sfogel_emdb/oracle/dbs/t_db1.f’ is media corrupt

Message       : Object BMRTEST1 owned by SYS might be unavailable

Finding

Finding Name  : Media Block Corruption

Finding ID    : 1071

Type          : FAILURE

Status        : OPEN

Priority      : HIGH

Message       : Block 64351 in datafile 1:

‘/ade/sfogel_emdb/oracle/dbs/t_db1.f’ is media corrupt

Message       : Object BMRTEST2 owned by SYS might be unavailable

Viewing Reports Using the ADRCI Utility

You can create and view Health Monitor checker reports using the ADRCI utility.

To create and view a checker report using ADRCI

  1. Ensure that operating system environment variables (such as ORACLE_HOME) are set properly, and then enter the following command at the operating system command prompt:

2.      ADRCI

The utility starts and displays the following prompt:

adrci>>

Optionally, you can change the current ADR home. Use the SHOW HOMES command to list all ADR homes, and the SET HOMEPATH command to change the current ADR home. See Oracle Database Utilities for more information.

3. Enter the following command:

show hm_run

This command lists all the checker runs (stored in V$HM_RUN) registered in the ADR repository.

4. Locate the checker run for which you want to create a report and note the checker run name. The REPORT_FILE field contains a filename if a report already exists for this checker run. Otherwise, generate the report with the following command:

5.      create report hm_run run_name

6. To view the report, enter the following command:

show report hm_run run_name

**  For more details regarding HM views, parameters and more see

http://download.oracle.com/docs/cd/B28359_01/server.111/b28310/diag007.htm

*** Reference Oracle® Database Administrator’s Guide 11g Release 1 (11.1)

Part Number B28310-04

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Oracle 11g GoldenGate and Compressed Tables

Posted by sdefilip on January 6, 2011

Oracle GoldenGate and Compressed Tables

OGG does not support compressed tables or partitions, neither does it handle it well with proper error messages until OGG v10.4. The abends may or may not produce any error message and sometimes produce wrong messages.

From V11.1.1.0.0, Oracle has enhanced the error handling part in BugDB 9425542, which gives meaningful error message on the compressed record before Extract abend. It will list out the table name, rowid, etc

Example :
ERROR OGG-01028 Record on table QATEST1.TAB1 with rowid AAM4EkAAEAACBguAAA from transaction 5.24.270123 (0x0005.018.00041f2b) is compressed. Compression is not supported.

However, due to bug 10063108, sometimes the error message on compressed tables are not entirely correct. This problem has been fixed in 11.1.1.0.3 and above

A table created as compressed will cause all of the DML’s to go into compressed blocks on disk. If the user does an “alter table nocompress”, every DML that goes into the table AFTER that point in time will be uncompressed. The query for compression will return “nocompress” now, but the simple “alter” does not change the already existing compressed blocks on disk that were created before the “alter”. So to capture the records from a table which was compressed we need to do the following

SQL> alter table move nocompress;

This will touch every single block on disk and will uncompress everything thereby causing OGG to work properly and not abend.

If there is even a single partition in a partitioned table that is compressed, it will cause an abend. Partition compression can be verified by getting the full DDL for the table by running the DBMS_METADATA.GET_DDL package. For table partitions that are compressed, run the below query and get the partition names & tablespace names.

SQL> SELECT partition_name, subpartition_name, tablespace_name, high_value FROM user_tab_subpartitions WHERE table_name = ‘table_name’;

Alter statement for partition to move to nocompress:

SQL> ALTER TABLE MOVE PARTITION NOCOMPRESS TABLESPACE ;

Eensure that you have enough disk space within your tablespaces before running the ALTER statement.

Support of compressed tables will be in future releases of OGG, however, in current V10.4 and V11.1.1.x, the only option, if a “move nocompress” is not possible, is to comment the compressed table or exclude them from the Extract.

Listing some scenarios in which we have seen similar errors for compression  :
1) The extract abends with the following error

GGS ERROR ZZ-0QY Failed to validate table <SCHEMA>.<TABLE NAME>. The table is compressed and extract will not be able to extract data from Oracle logs.

This bug happens when DDL is enabled, the checking was not done correctly when table resides on Bigfile tablespace.

Issue is fixed in V10.4.0.93 and V11.1.1.0.4

Reference bugdb – 10063075

2) When running with OGG version earlier than V11.1.1.0.10, Extract might abend with below error message, without telling the name of the table or the Objectid of the compressed table

Source Context :

SourceModule : [er.redo.ora.sr]
SourceID : [/mnt/ecloud/workspace/Build_OpenSys_r11.1.1.0.9_004
_[40043]/perforce/src/app/er/redo/oracle/redoorasr.c]
SourceFunction : [get_subrec(int32_t, mempool_t *, unsigned char *, u
nsigned short, subrec_info_t *, redo_thread_t *, BOOL, log_context_t *)]
SourceLine : [5434]

2010-11-10 11:50:26 ERROR OGG-01028 compressed tables are not supported.

This is because there is a temp table created as compressed, then followed directly by a direct load operation.

Try to exclude the table DBMS_TABCOMP_TEMP_UNCMP and DBMS_TABCOMP_TEMP_CMP, which was created by Compression advisory.

From OGG v11.1.1.0.10 onwards when the extract abends because of direct load inserts on tables with compressed partitions, the extract gives the table name in the error.

Reference bugdb – 10279456

However, if the table has been dropped immediately after creation, the Extract will only give out the object ID of the “compressed” table.  To find out exactly what was the compressed table name, you could query GGS_DDL_HIST table if DDL replication is enabled.  A sample query

select OBJECTID, OBJECTNAME, METADATA_TEXT FROM GGS_DDL_HIST WHERE OBJECTID = xxxxx

 

 

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