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31 DBMS_COMPARISON

The DBMS_COMPARISON package provides interfaces to compare and converge database objects at different databases.

This chapter contains the following topics:

See Also:


Using DBMS_COMPARISON

This section contains topics which relate to using the DBMS_COMPARISON package.


Overview

The DBMS_COMPARISON package is an Oracle-supplied package that you can use to compare database objects at two databases. This package also enables you converge the database objects so that they are consistent at different databases. Typically, this package is used in environments that share a database object at multiple databases. When copies of the same database object exist at multiple databases, the database object is a shared database object. Several data dictionary views contain information about comparisons made with the DBMS_COMPARISON package.

Shared database objects might be maintained by data replication. For example, materialized views or Oracle Streams components might replicate the database objects and maintain them at multiple databases. A custom application might also maintain shared database objects. When a database object is shared, it can diverge at the databases that share it. You can use this package to identify differences in the shared database objects. After identifying the differences, you can optionally use this package to synchronize the shared database objects.

To compare a database object that is shared at two different databases, complete the following general steps:

  1. Run the CREATE_COMPARE procedure in this package to create a comparison. The comparison identifies the database objects to compare and specifies parameters for the comparison.

  2. Run the COMPARE function in this package to compare the database object at the two databases and identify differences. This function returns TRUE when no differences are found and FALSE when differences are found. This function also populates data dictionary views with comparison results. Separate comparison results are generated for each execution of the COMPARE function.

  3. If you want to examine the comparison results, query the following data dictionary views:

    • DBA_COMPARISON_SCAN

    • USER_COMPARISON_SCAN

    • DBA_COMPARISON_SCAN_SUMMARY

    • USER_COMPARISON_SCAN_SUMMARY

    • DBA_COMPARISON_SCAN_VALUES

    • USER_COMPARISON_SCAN_VALUES

    • DBA_COMPARISON_ROW_DIF

    • USER_COMPARISON_ROW_DIF

  4. If there are differences, and you want to synchronize the database objects at the two databases, then run the CONVERGE procedure in this package.

After you create a comparison with the CREATE_COMPARISON procedure in the DBMS_COMPARISON package, you can run the comparison at any time using the COMPARE function. Each time you run the COMPARE function, it records comparison results in the appropriate data dictionary views. Comparison results might be modified when subprograms in this package are invoked and the scans in the comparison results are specified. For example, comparison results might be modified when you run the RECHECK function.

The comparison results for a single execution of the COMPARE function can include one or more scans. A scan checks for differences in some or all of the rows in a shared database object at a single point in time. You can compare database objects multiple times, and a unique scan ID identifies each scan in the comparison results.

A bucket is a range of rows in a database object that is being compared. Buckets improve performance by splitting the database object into ranges and comparing the ranges independently. Every comparison divides the rows being compared into an appropriate number of buckets, and each bucket is compared by a scan.

Each time the COMPARE function splits a bucket into smaller buckets, it performs new scans of the smaller buckets. The scan that analyzes a larger bucket is the parent scan of each scan that analyzes the smaller buckets into which the larger bucket was split. The root scan in the comparison results is the highest level parent scan. The root scan does not have a parent.

You can recheck a scan using the RECHECK function, and you can converge a scan using the CONVERGE procedure. When you want to recheck or converge all of the rows comparison results, specify the root scan ID for the comparison results in the appropriate subprogram. When you want to recheck or converge a portion of the rows in comparison results, specify the scan ID of the scan that contains the differences.

See Also:

Oracle Streams Replication Administrator's Guide for more information about comparisons, including detailed information about scans, buckets, parent scans, and root scans

Security Model

Security on this package can be controlled in either of the following ways:

If subprograms in the package are run from within a stored procedure, then the user who runs the subprograms must be granted EXECUTE privilege on the package directly. It cannot be granted through a role.

Each subprogram in the DBMS_COMPARISON package has a comparison_name parameter. The current user must be the owner of the specified comparison to run a subprogram in the DBMS_COMPARISON package.

To run the COMPARE function, RECHECK function, or CONVERGE procedure, the following users must have SELECT privilege on each copy of the shared database object:

The CONVERGE procedure also requires additional privileges for one of these users at the database where it makes changes to the shared database object. The user must have INSERT, UPDATE, and DELETE privileges on the shared database object at this database.


Constants

The DBMS_COMPARISON package defines several enumerated constants that should be used for specifying parameter values. Enumerated constants must be prefixed with the package name. For example, DBMS_COMPARISON.CMP_SCAN_MODE_FULL.

Table 31-1 lists the parameters and enumerated constants.

Table 31-1 DBMS_COMPARISON Parameters with Enumerated Constants

Parameter Option Type Description

comparison_mode

  • CMP_COMPARE_MODE_OBJECT

VARCHAR2(30)

CMP_COMPARE_MODE_OBJECT is a database object. This constant can be specified as 'OBJECT'.

scan_mode

  • CMP_SCAN_MODE_FULL

  • CMP_SCAN_MODE_RANDOM

  • CMP_SCAN_MODE_CYCLIC

  • CMP_SCAN_MODE_CUSTOM

VARCHAR2(30)

CMP_SCAN_MODE_FULL indicates that the entire database object is compared. This constant can be specified as 'FULL'.

CMP_SCAN_MODE_RANDOM indicates that a random portion of the database object is compared. This constant can be specified as 'RANDOM'.

CMP_SCAN_MODE_CYCLIC indicates that a portion of the database object is compared when you perform a single comparison. When you compare the database object again, another portion of the database object is compared, starting where the last comparison ended. This constant can be specified as 'CYCLIC'.

CMP_SCAN_MODE_CUSTOM indicates that the user who runs the subprogram specifies the range to compare in the database object. This constant can be specified as 'CUSTOM'.

converge_options

  • CMP_CONVERGE_LOCAL_WINS

  • CMP_CONVERGE_REMOTE_WINS

VARCHAR2(30)

CMP_CONVERGE_LOCAL_WINS indicates that the column values at the local database replace the column values at the remote database when these column values are different. This constant can be specified as 'LOCAL'.

CMP_CONVERGE_REMOTE_WINS indicates that the column values at the remote database replace the column values at the local database when these column values are different. This constant can be specified as 'REMOTE'.

null_value

  • CMP_NULL_VALUE_DEF

VARCHAR2(100)

CMP_NULL_VALUE_DEF indicates that ORA$STREAMS$NV is substituted for NULL values in database objects during comparison. This constant can be specified as 'ORA$STREAMS$NV'.

max_num_buckets

  • CMP_MAX_NUM_BUCKETS

INTEGER

CMP_MAX_NUM_BUCKETS indicates that the maximum number of buckets is 1,000. This constant can be specified as 1000.

min_rows_in_bucket

  • CMP_MIN_ROWS_IN_BUCKET

INTEGER

CMP_MIN_ROWS_IN_BUCKET indicates that the minimum number of rows in a bucket is 10,000. This constant can be specified as 10000.



Views

The DBMS_COMPARISON package uses the following views:


Operational Notes

This section contains the following operational notes for the DBMS_COMPARISON package:

Oracle Database Release Requirements for the DBMS_COMPARISON Package

Meet the following Oracle Database release requirements when running the subprograms in the DBMS_COMPARISON package:

Database Character Set Requirements for the DBMS_COMPARISON Package

The database character sets must be the same for the databases that contain the database objects being compared.

See Also:

Oracle Database Globalization Support Guide for information about database character sets

Database Object Requirements for the DBMS_COMPARISON Package

The DBMS_COMPARISON package can compare the following types of database objects:

Database objects of different types can be compared and converged at different databases. For example, a table at one database and a materialized view at another database can be compared and converged with this package.

To run the subprograms in the DBMS_COMPARISON package, the specified database objects must have the same shape at each database. Specifically, the database objects must have the same number of columns at each database, and the datatypes of corresponding columns must match.

If a database object being compared contains columns that do not exist in the other database object, then you can compare the database objects by excluding the extra columns during comparison creation. Use the column_list parameter in the CREATE_COMPARISON procedure to list only the columns that exist in both database objects.

Index Column Requirements for the DBMS_COMPARISON Package

This section discusses number, timestamp, and interval columns. These include the following datatypes:

For all scan modes to be supported by the DBMS_COMPARISON package, the database objects must have one of the following types of indexes:

For the scan modes CMP_SCAN_MODE_FULL and CMP_SCAN_MODE_CUSTOM to be supported, the database objects must have one of the following types of indexes:

If the database objects do not have one of these types of indexes, then the DBMS_COMPARISON package does not support the database objects. For example, if the database objects only have a single index on an NVARCHAR2 column, then the DBMS_COMPARISON package does not support them. Or, if the database objects have only one index, and it is a composite index that includes a NUMBER column and an NCHAR column, then the DBMS_COMPARISON package does not support them.

You can specify an index when you create a comparison using the index_schema_name and index_name parameters in the CREATE_COMPARISON procedure. If you specify an index, then make sure the columns in the index meet the requirements of the scan mode used for the comparison.

The index columns in a comparison must uniquely identify every row involved in a comparison. The following constraints satisfy this requirement:

If these constraints are not present on a table, then use the index_schema_name and index_name parameters in the CREATE_COMPARISON procedure to specify an index whose columns satisfy this requirement.

The DBMS_COMPARISON package can use an index only if all of the columns in the index are included in the column_list parameter when the comparison is created with the CREATE_COMPARISON procedure.

After a comparison is created, you can determine the index column or columns for it by running the following query:

SELECT COLUMN_NAME, COLUMN_POSITION FROM DBA_COMPARISON_COLUMNS 
  WHERE COMPARISON_NAME = 'COMPARE_CUSTOM' AND
        INDEX_COLUMN    = 'Y';

If there is more than one index column, then the index column with 1 for the COLUMN_POSITION is the lead index column in the composite index.

See Also:

Datatype Requirements for the DBMS_COMPARISON Package

The DBMS_COMPARISON package can compare data in columns of the following datatypes:

If a column with datatype TIMESTAMP WITH LOCAL TIME ZONE is compared, then the two databases must use the same time zone. Also, if a column with datatype NVARCHAR2 or NCHAR is compared, then the two databases must use the same national character set.

The DBMS_COMPARISON package cannot compare data in columns of the following datatypes:

You can compare database objects that contain unsupported columns by excluding the unsupported columns during comparison creation. Use the column_list parameter in the CREATE_COMPARISON procedure to list only the supported columns in a shared database object.

See Also:

Only Converge Rows That Are Not Being Updated

You should only converge rows that are not being updated on either database. For example, if the shared database object is updated by replication components, then only converge rows for which replication changes have already been applied and make sure no new changes are in the process of being replicated for these rows. If you compare replicated database objects, then it is typically best to compare them during a time of little or no replication activity to identify persistent differences.

Attention:

If a scan identifies that a row is different in the shared database object at two databases, and the row is modified after the scan, then it can result in unexpected data in the row after the CONVERGE procedure is run.

See Also:

Oracle Streams Replication Administrator's Guide for information about the DBMS_COMPARISON package in an Oracle Streams replication environment

Data Structures

The DBMS_COMPARISON package defines a RECORD type.

RECORD Types


COMPARISON_TYPE Record Type

Contains information returned by the COMPARE function or CONVERGE procedure in the DBMS_COMPARISON package.

Note:

The COMPARE function only returns a value for the scan_id field.

Syntax

TYPE COMPARISON_TYPE IS RECORD(
  scan_id            NUMBER,
  loc_rows_merged    NUMBER,
  rmt_rows_merged    NUMBER,
  loc_rows_deleted   NUMBER,
  rmt_rows_deleted   NUMBER);

Fields

Table 31-2 COMPARISON_TYPE Attributes

Field Description

scan_id

The scan ID of the scan

loc_rows_merged

The number of rows in the local database object updated with information from the database object at the remote site

rmt_rows_merged

The number of rows in the database object updated at the remote site with information from the database object at the local site

loc_rows_deleted

The number of rows deleted from the local database object

rmt_rows_deleted

The number of rows deleted from the remote database object



Summary of DBMS_COMPARISON Subprograms

Table 31-3 DBMS_COMPARISON Package Subprograms

Subprogram Description

COMPARE Function

Performs the specified comparison

CONVERGE Procedure

Executes data manipulation language (DML) changes to synchronize the portion of the database object that was compared in the specified scan

CREATE_COMPARISON Procedure

Creates a comparison

DROP_COMPARISON Procedure

Drops a comparison

PURGE_COMPARISON Procedure

Purges the comparison results, or a subset of the comparison results, for a comparison

RECHECK Function

Rechecks the differences in a specified scan for a comparison



COMPARE Function

This function performs the specified comparison.

Each time a comparison is performed, it results in at least one new scan, and each scan has a unique scan ID. You can define and name a comparison using the CREATE_COMPARISON procedure.

Syntax

DBMS_COMPARISON.COMPARE(
   comparison_name  IN   VARCHAR2,
   scan_info        OUT  COMPARISON_TYPE,
   min_value        IN   VARCHAR2   DEFAULT NULL,
   max_value        IN   VARCHAR2   DEFAULT NULL,
   perform_row_dif  IN   BOOLEAN    DEFAULT FALSE)
RETURN BOOLEAN;

Parameters

Table 31-4 COMPARE Function Parameters

Parameter Description

comparison_name

The name of the comparison.

scan_info

Information about the compare operation returned in the COMPARISON_TYPE datatype.

See COMPARISON_TYPE Record Type.

min_value

When the scan mode for the comparison is set to CMP_SCAN_MODE_CUSTOM, specify the minimum index column value for the range of rows that are being compared. To determine the index column for a comparison, query the DBA_COMPARISON_COLUMNS data dictionary view. For a composite index, specify a value for the column with column_position equal to 1 in the DBA_COMPARISON_COLUMNS view. See "Index Column Requirements for the DBMS_COMPARISON Package".

If the scan mode is set to a value other than CMP_SCAN_MODE_CUSTOM, then this parameter must be set to NULL.

If NULL and the scan_mode parameter is set to CMP_SCAN_MODE_CUSTOM, then an error is raised.

To determine the scan mode for the comparison, query the DBA_COMPARISON data dictionary view.

See Constants for information about scan modes.

max_value

When the scan mode for the comparison is set to CMP_SCAN_MODE_CUSTOM, specify the maximum index column value for the range of rows that are being compared. To determine the index column for a comparison, query the DBA_COMPARISON_COLUMNS data dictionary view. For a composite index, specify a value for the column with column_position equal to 1 in the DBA_COMPARISON_COLUMNS view. See "Index Column Requirements for the DBMS_COMPARISON Package".

If the scan mode is set to a value other than CMP_SCAN_MODE_CUSTOM, then this parameter must be set to NULL.

If NULL and the scan_mode parameter is set to CMP_SCAN_MODE_CUSTOM, then an error is raised.

To determine the scan mode for the comparison, query the DBA_COMPARISON data dictionary view.

See Constants for information about scan modes.

perform_row_dif

If TRUE, then compares each row individually in the database object being compared after reaching the smallest possible bucket for the comparison.

If FALSE, then compares buckets for differences but does not compare each row individually when differences are found in the smallest possible bucket.

See "Overview" for information about buckets.


Return Values

This function returns TRUE when no differences are found in the database objects being compared. This function returns FALSE when differences are found in the database objects being compared.


CONVERGE Procedure

This procedure executes data manipulation language (DML) changes to synchronize the portion of the database objects that was compared in the specified scan.

Syntax

DBMS_COMPARISON.CONVERGE(
   comparison_name      IN   VARCHAR2,
   scan_id              IN   NUMBER,
   scan_info            OUT  COMPARISON_TYPE,
   converge_options     IN   VARCHAR2  DEFAULT CMP_CONVERGE_LOCAL_WINS,
   perform_commit       IN   BOOLEAN   DEFAULT TRUE,
   local_converge_tag   IN   RAW       DEFAULT NULL,
   remote_converge_tag  IN   RAW       DEFAULT NULL);

Parameters

Table 31-5 CONVERGE Procedure Parameters

Parameter Description

comparison_name

The name of the comparison.

scan_id

The identifier for the scan that contains the differences between the database objects being converged.

See "Overview" for more information about specifying a scan ID in this parameter.

scan_info

Information about the converge operation returned in the COMPARISON_TYPE datatype.

See COMPARISON_TYPE Record Type.

converge_options

Either the CMP_CONVERGE_LOCAL_WINS constant or the CMP_CONVERGE_REMOTE_WINS constant.

See "Constants" for information about these constants.

perform_commit

If TRUE, then performs a COMMIT periodically while making the DML changes. The CONVERGE procedure might perform more than one COMMIT when this parameter is set to TRUE.

If FALSE, then does not perform a COMMIT after making DML changes

local_converge_tag

The Oracle Streams tag to set in the session on the local database before performing any changes to converge the data in the database objects being converged.

If non-NULL, then this parameter setting takes precedence over the local_converge_tag parameter in the CREATE_COMPARISON procedure that created the comparison.

If NULL, then this parameter is ignored, and the local_converge_tag parameter in the CREATE_COMPARISON procedure that created the comparison is used.

See the Oracle Streams Replication Administrator's Guide for more information about tags.

remote_converge_tag

The Oracle Streams tag to set in the session on the remote database before performing any changes to converge the data in the database objects being converged.

If non-NULL, then this parameter setting takes precedence over the remote_converge_tag parameter in the CREATE_COMPARISON procedure that created the comparison.

If NULL, then this parameter is ignored, and the remote_converge_tag parameter in the CREATE_COMPARISON procedure that created the comparison is used.

See the Oracle Streams Replication Administrator's Guide for more information about tags.


Usage Notes

If one of the database objects being converged is a read-only materialized view, then the converge_options parameter must be set to ensure that the read-only materialized view "wins" in the converge operation. The CONVERGE procedure raises an error if it tries to make changes to a read-only materialized view.


CREATE_COMPARISON Procedure

This procedure creates a comparison.

Syntax

DBMS_COMPARISON.CREATE_COMPARISON(
   comparison_name      IN  VARCHAR2,
   schema_name          IN  VARCHAR2,
   object_name          IN  VARCHAR2,
   dblink_name          IN  VARCHAR2,
   index_schema_name    IN  VARCHAR2  DEFAULT NULL,
   index_name           IN  VARCHAR2  DEFAULT NULL,
   remote_schema_name   IN  VARCHAR2  DEFAULT NULL,
   remote_object_name   IN  VARCHAR2  DEFAULT NULL,
   comparison_mode      IN  VARCHAR2  DEFAULT CMP_COMPARE_MODE_OBJECT,
   column_list          IN  VARCHAR2  DEFAULT '*',
   scan_mode            IN  VARCHAR2  DEFAULT CMP_SCAN_MODE_FULL,
   scan_percent         IN  NUMBER    DEFAULT NULL,
   null_value           IN  VARCHAR2  DEFAULT CMP_NULL_VALUE_DEF,
   local_converge_tag   IN  RAW       DEFAULT NULL,
   remote_converge_tag  IN  RAW       DEFAULT NULL,
   max_num_buckets      IN  NUMBER    DEFAULT CMP_MAX_NUM_BUCKETS,
   min_rows_in_bucket   IN  NUMBER    DEFAULT CMP_MIN_ROWS_IN_BUCKET);

Parameters

Table 31-6 CREATE_COMPARISON Procedure Parameters

Parameter Description

comparison_name

The name of the comparison.

schema_name

The name of the schema that contains the local database object to compare.

object_name

The name of the local database object to compare.

dblink_name

Database link to the remote database. The specified database object in the remote database is compared with the database object in the local database.

If NULL, then the comparison is configured to compare two database objects in the local database. In this case, parameters that specify the remote database object apply to the second database object in the comparison and to operations on the second database object. For example, specify the second database object in this procedure by using the remote_schema_name and remote_object_name parameters.

index_schema_name

The name of the schema that contains the index.

If NULL, then the schema specified in the schema_name parameter is used.

index_name

The name of the index.

If NULL, then the system determines the index columns for the comparison automatically.

If the index_schema_name parameter is non-NULL, then the index_name parameter must also be non-NULL. Otherwise, an error is raised.

See Also: "Usage Notes" for more information about specifying an index

remote_schema_name

The name of the schema that contains the database object at the remote database. Specify a non-NULL value if the schema names are different at the two databases.

If NULL, then the schema specified in the schema_name parameter is used.

remote_object_name

The name of the database object at the remote database. Specify a non-NULL value if the database object names are different at the two databases.

If NULL, then the database object specified in the object_name parameter is used.

comparison_mode

Specify the default value CMP_COMPARE_MODE_OBJECT. Additional modes might be added in future releases.

column_list

Specify '*' to include all of the columns in the database objects being compared.

To compare a subset of columns in the database objects, specify a comma-separated list of the columns to check. Any columns that are not in the list are ignored during a comparison and convergence.

See "Usage Notes" for information about columns that are required in the column_list parameter.

scan_mode

Either CMP_SCAN_MODE_FULL, CMP_SCAN_MODE_RANDOM, CMP_SCAN_MODE_CYCLIC, or CMP_SCAN_MODE_CUSTOM.

If you specify CMP_SCAN_MODE_CUSTOM, then make sure you specify an index using the index_schema_name and index_name parameters. Specifying an index ensures that you can specify the correct min_value and max_value for the lead index column when you run the COMPARE or RECHECK function.

See "Constants" for information about these constants.

scan_percent

The percentage of the database object to scan for comparison when the scan_mode parameter is set to either CMP_SCAN_MODE_RANDOM or CMP_SCAN_MODE_CYCLIC. For these scan_mode settings, a non-NULL value that is greater than 0 (zero) and less than 100 is required.

If NULL and the scan_mode parameter is set to CMP_SCAN_MODE_FULL, then the entire database object is scanned for comparison.

If NULL and the scan_mode parameter is set to CMP_SCAN_MODE_CUSTOM, then the portion of the database object scanned for comparison is specified when the COMPARE function is run.

If non-NULL and the scan_mode parameter is set to either CMP_SCAN_MODE_FULL or CMP_SCAN_MODE_CUSTOM, then the scan_percent parameter is ignored.

Note: When the scan_percent parameter is non-NULL, and the lead index column for the comparison does not distribute the rows in the database object evenly, the portion of the database object that is compared might be smaller or larger than the specified scan_percent value. See "Index Column Requirements for the DBMS_COMPARISON Package" for more information about the lead index column.

null_value

The value to substitute for each NULL in the database objects being compared. Specify a value or use the CMP_NULL_VALUE_DEF constant.

If a column being compared can contain NULLs, then the value specified for this parameter must be different than any non-NULL value in the column. Otherwise, if the value specified for this parameter can appear in the column, some row differences might not be found.

See "Constants" for information about this constant.

local_converge_tag

The Oracle Streams tag to set in the session on the local database before performing any changes to converge the data in the database objects being compared.

If the local_converge_tag parameter is non-NULL in the CONVERGE procedure when comparison results for this comparison are converged, then the setting in the CONVERGE procedure takes precedence. See CONVERGE Procedure for more information.

See the Oracle Streams Replication Administrator's Guide for more information about tags.

remote_converge_tag

The Oracle Streams tag to set in the session on the remote database before performing any changes to converge the data in the database objects being compared.

If the remote_converge_tag parameter is non-NULL in the CONVERGE procedure when comparison results for this comparison are converged, then the setting in the CONVERGE procedure takes precedence. See CONVERGE Procedure for more information.

See the Oracle Streams Replication Administrator's Guide for more information about tags.

max_num_buckets

Specify the maximum number of buckets to use. Specify a value or use the CMP_MAX_NUM_BUCKETS constant. See "Constants" for information about this constant.

See "Overview" for information about buckets.

Note: If an index column for a comparison is a VARCHAR2 or CHAR column, then the number of buckets might exceed the value specified for the max_num_buckets parameter.

min_rows_in_bucket

Specify the minimum number of rows in each bucket. Specify a value or use the CMP_MIN_ROWS_IN_BUCKET constant. See "Constants" for information about this constant.

See "Overview" for information about buckets.


Usage Notes

This section contains usage notes for the CREATE_COMPARISON procedure.

Usage Notes for the index_schema_name and index_name Parameters

When you specify an index for a comparison with the index_schema_name and index_name parameters, the specified index determines the comparison's index columns and their ordering. The order of the columns in the index determines the index column ordering for the comparison. Therefore, the column in column position 1 in the index is the lead column for the comparison.

The index columns and their ordering affect the details of each SQL statement generated and executed for a comparison. For each SQL statement, the optimizer decides whether or not to use indexes. If the optimizer decides to use indexes, then the optimizer decides which particular indexes to use. An index specified in column_list parameter might or might not be used.

The columns in the specified index must meet the requirements described in "Index Column Requirements for the DBMS_COMPARISON Package". If the index columns do not meet these requirements, then an error is raised.

Usage Notes for the column_list Parameter

When the column_list parameter is set to a value other than '*', the following columns are required in the column_list parameter:


DROP_COMPARISON Procedure

This procedure drops a comparison.

Syntax

DBMS_COMPARISON.DROP_COMPARISON(
   comparison_name  IN  VARCHAR2);

Parameters

Table 31-7 DROP_COMPARISON Procedure Parameters

Parameter Description

comparison_name

The name of the comparison.



PURGE_COMPARISON Procedure

This procedure purges the comparison results, or a subset of the comparison results, for a comparison.

Note:

At least one of the following parameters must be set to NULL: scan_id or purge_time. If both the scan_id and purge_time parameters are NULL, then this procedure purges all comparison results for the comparison.

Syntax

DBMS_COMPARISON.PURGE_COMPARISON(
   comparison_name  IN  VARCHAR2,
   scan_id          IN  NUMBER     DEFAULT NULL,
   purge_time       IN  TIMESTAMP  DEFAULT NULL);

Parameters

Table 31-8 PURGE_COMPARISON Procedure Parameters

Parameter Description

comparison_name

The name of the comparison.

scan_id

The scan ID of the scan for which results are purged. The scan ID must identify a root scan. If the scan ID does not identify a root scan, then an error is raised. When a root scan ID is specified, it is purged, and all direct and indirect child scans of the specified root scan are purged.

If NULL, then no scan ID is considered when purging comparison results for the comparison.

See "Overview" for information about scans.

purge_time

The date before which results are purged.

If NULL, then no date is considered when purging comparison results for the comparison.



RECHECK Function

This function rechecks the differences in a specified scan for a comparison.

This function performs one of the following actions:

Note:

This function does not compare the shared database object for differences that were not recorded in the specified comparison scan. To check for those differences, run the COMPARE function.

Syntax

DBMS_COMPARISON.RECHECK(
   comparison_name  IN  VARCHAR2,
   scan_id          IN  NUMBER,
   perform_row_dif  IN  BOOLEAN  DEFAULT FALSE)
RETURN BOOLEAN;

Parameters

Table 31-9 RECHECK Function Parameters

Parameter Description

comparison_name

The name of the comparison.

scan_id

The scan ID of the scan to recheck.

See "Overview" for more information about specifying a scan ID in this parameter.

perform_row_dif

If TRUE, then compares each row individually in the database objects being compared after reaching the smallest possible bucket for the comparison.

If FALSE, then compares buckets for differences but does not compare each row individually when differences are found in the smallest possible bucket.

See "Overview" for information about buckets.


Return Values

This function returns TRUE when no differences are found in the database objects being compared. This function returns FALSE when differences are found in the database objects being compared.