Running Health Checks with Health Monitor

About Health Monitor Checks

Health Monitor checks (also known as checkers, health checks, or checks) examine various layers and components of the database. Health checks detect file corruptions, physical and logical block corruptions, undo and redo corruptions, data dictionary corruptions, and more. The health checks generate reports of their findings and, in many cases, recommendations for resolving problems. Health checks can be run in two ways:

• Reactive—The fault diagnosability infrastructure can run health checks automatically in response to a critical error.

• Manual—As a DBA, you can manually run health checks using either the DBMS_HM PL/SQL package or the Enterprise Manager interface. You can run checkers on a regular basis if desired, or Oracle Support may ask you to run a checker while working with you on a service request.

Health Monitor checks store findings, recommendations, and other information in the Automatic Diagnostic Repository (ADR).

Health checks can run in two modes:

• DB-online mode means the check can be run while the database is open (that is, in OPEN mode or MOUNT mode).

• DB-offline mode means the check can be run when the instance is available but the database itself is closed (that is, in NOMOUNT mode).

All the health checks can be run in DB-online mode. Only the Redo Integrity Check and the DB Structure Integrity Check can be used in DB-offline mode.

Types of Health Checks

Health monitor runs the following checks:

• DB Structure Integrity Check—This check verifies the integrity of database files and 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.

• Data Block Integrity Check—This check 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.

• Redo Integrity Check—This check 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.

• Undo Segment Integrity Check—This check 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—This check is identical to the Undo Segment Integrity Check except that it checks only one specific transaction.

• Dictionary Integrity Check—This check 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$, and ecol$.

Running Health Checks Using the DBMS_HM PL/SQL Package

The DBMS_HM procedure for running a health check is called RUN_CHECK. To call RUN_CHECK, supply the name of the check and a name for the run, as follows:

BEGIN
  DBMS_HM.RUN_CHECK('Dictionary Integrity Check', 'my_run');
END;
/

To obtain a list of health check names, run the following query:

SELECT name FROM v$hm_check WHERE internal_check='N';

NAME
----------------------------------------------------------------
DB Structure Integrity Check
Data Block Integrity Check
Redo Integrity Check
Transaction Integrity Check
Undo Segment Integrity Check
Dictionary Integrity 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 Health Checks Using Enterprise Manager

Enterprise Manager provides an interface for running Health Monitor checkers.

To run a Health Monitor 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 Reports Using Enterprise Manager

You can also view Health Monitor reports and findings for a given checker run using Enterprise Manager.

To view run findings using Enterprise Manager

1. Access the Database Home page.

   For Oracle Enterprise Manager Database Control, see Oracle Database 2 Day DBA for instructions. For Oracle Enterprise Manager Grid Control, go to the desired database target.

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.

5. Click Runs to display the Runs subpage.

   Enterprise Manager displays more information about the checker run.

6. 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                   : 2007-05-12 22:11:02.032292 -07:00
 End Time                     : 2007-05-12 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:
               '/u01/app/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:
               '/u01/app/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:

   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.

2. Enter the following command:

   show hm_run
   

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

3. 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:

   create report hm_run run_name
   

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

   show report hm_run run_name