17 DBMS_REFRESH

DBMS_REFRESH enables you to create groups of materialized views that can be refreshed together to a transactionally consistent point in time.

This chapter contains this topic:

Summary of DBMS_REFRESH Subprograms

Summary of DBMS_REFRESH Subprograms

Table 17-1 DBMS_REFRESH Package Subprograms

Subprogram	Description
"ADD Procedure"	Adds materialized views to a refresh group.
"CHANGE Procedure"	Changes the refresh interval for a refresh group.
"DESTROY Procedure"	Removes all of the materialized views from a refresh group and deletes the refresh group.
"MAKE Procedure"	Specifies the members of a refresh group and the time interval used to determine when the members of this group should be refreshed.
"REFRESH Procedure"	Manually refreshes a refresh group.
"SUBTRACT Procedure"	Removes materialized views from a refresh group.

ADD Procedure

This procedure adds materialized views to a refresh group.

See Also:

Step 6, "Add objects to the refresh group.", and Oracle Database Advanced Replication for more information

Syntax

DBMS_REFRESH.ADD (
   name     IN VARCHAR2,
   { list   IN VARCHAR2, 
   | tab    IN DBMS_UTILITY.UNCL_ARRAY, }
   lax      IN BOOLEAN := FALSE);

Note:

This procedure is overloaded. The list and tab parameters are mutually exclusive.

Parameters

Table 17-2 ADD Procedures Parameters

Parameter	Description
name	Name of the refresh group to which you want to add members, specified as `[schema_name.]refresh_group_name`. If the schema is not specified, then the current user is the default.
list	Comma-delimited list of materialized views that you want to add to the refresh group. Synonyms are not supported. Each materialized view is specified as `[schema_name.]materialized_view_name`. If the schema is not specified, then the refresh group owner is the default.
tab	Instead of a comma-delimited list, you can supply a PL/SQL index-by table of type `DBMS_UTILITY`.`UNCL_ARRAY`, where each element is the name of a materialized view. The first materialized view should be in position 1. The last position must be `NULL`. Each materialized view is specified as `[schema_name.]materialized_view_name`. If the schema is not specified, then the refresh group owner is the default.
lax	A materialized view can belong to only one refresh group at a time. If you are moving a materialized view from one group to another, then you must set the `lax` flag to `TRUE` to succeed. Oracle then automatically removes the materialized view from the other refresh group and updates its refresh interval to be that of its new group. Otherwise, the call to `ADD` generates an error message.

CHANGE Procedure

This procedure changes the refresh interval for a refresh group.

See Also:

Oracle Database Advanced Replication for more information about refresh groups

Syntax

DBMS_REFRESH.CHANGE (
   name                  IN VARCHAR2,
   next_date             IN DATE           := NULL,
   interval              IN VARCHAR2       := NULL,
   implicit_destroy      IN BOOLEAN        := NULL,
   rollback_seg          IN VARCHAR2       := NULL,
   push_deferred_rpc     IN BOOLEAN        := NULL,
   refresh_after_errors  IN BOOLEAN        := NULL,
   purge_option          IN BINARY_INTEGER := NULL,
   parallelism           IN BINARY_INTEGER := NULL,
   heap_size             IN BINARY_INTEGER := NULL);

Parameters

Table 17-3 CHANGE Procedures Parameters

Parameter	Description
name	Name of the refresh group for which you want to alter the refresh interval.
next_date	Next date that you want a refresh to occur. By default, this date remains unchanged.
interval	Function used to calculate the next time to refresh the materialized views in the refresh group. This interval is evaluated immediately before the refresh. Thus, you should select an interval that is greater than the time it takes to perform a refresh. By default, the interval remains unchanged.
implicit_destroy	Allows you to reset the value of the `implicit_destroy` flag. If this flag is set, then Oracle automatically deletes the group if it no longer contains any members. By default, this flag remains unchanged.
rollback_seg	Allows you to change the rollback segment used. By default, the rollback segment remains unchanged. To reset this parameter to use the default rollback segment, specify `NULL`, including the quotes. Specifying `NULL` without quotes indicates that you do not want to change the rollback segment currently being used.
push_deferred_rpc	Used by updatable materialized views only. Set this parameter to `TRUE` if you want to push changes from the materialized view to its associated master table or master materialized view before refreshing the materialized view. Otherwise, these changes might appear to be temporarily lost. By default, this flag remains unchanged.
refresh_after_errors	Used by updatable materialized views only. Set this parameter to `TRUE` if you want the refresh to proceed even if there are outstanding conflicts logged in the `DEFERROR` view for the materialized view's master table or master materialized view. By default, this flag remains unchanged.
purge_option	If you are using the parallel propagation mechanism (that is, `parallelism` is set to 1 or greater), then: 0 = do not purge 1 = lazy (default) 2 = aggressive In most cases, lazy purge is the optimal setting. Set purge to aggressive to trim back the queue if multiple master replication groups are pushed to different target sites, and updates to one or more replication groups are infrequent and infrequently pushed. If all replication groups are infrequently updated and pushed, then set purge to do not purge and occasionally execute `PUSH` with purge set to aggressive to reduce the queue.
parallelism	0 specifies serial propagation. n > 1 specifies parallel propagation with n parallel processes. 1 specifies parallel propagation using only one parallel process.
heap_size	Maximum number of transactions to be examined simultaneously for parallel propagation scheduling. Oracle automatically calculates the default setting for optimal performance. Note: Do not set this parameter unless directed to do so by Oracle Support Services.

DESTROY Procedure

This procedure removes all of the materialized views from a refresh group and delete the refresh group.

See Also:

Oracle Database Advanced Replication for more information refresh groups

Syntax

DBMS_REFRESH.DESTROY (
   name   IN   VARCHAR2);

Parameters

Table 17-4 DESTROY Procedure Parameters

Parameter	Description
name	Name of the refresh group that you want to destroy.

MAKE Procedure

This procedure specifies the members of a refresh group and the time interval used to determine when the members of this group should be refreshed.

See Also:

Step 4, "Create the refresh group.", and Oracle Database Advanced Replication for more information

Syntax

DBMS_REFRESH.MAKE (
   name                  IN    VARCHAR2
   { list                IN    VARCHAR2,
   | tab                 IN    DBMS_UTILITY.UNCL_ARRAY,}
   next_date             IN    DATE,
   interval              IN    VARCHAR2,
   implicit_destroy      IN    BOOLEAN         := FALSE,
   lax                   IN    BOOLEAN         := FALSE,
   job                   IN    BINARY_INTEGER  := 0,
   rollback_seg          IN    VARCHAR2        := NULL,
   push_deferred_rpc     IN    BOOLEAN         := TRUE,
   refresh_after_errors  IN    BOOLEAN         := FALSE
   purge_option          IN    BINARY_INTEGER  := NULL,
   parallelism           IN    BINARY_INTEGER  := NULL,
   heap_size             IN    BINARY_INTEGER  := NULL);

Note:

This procedure is overloaded. The list and tab parameters are mutually exclusive.

Parameters

Table 17-5 MAKE Procedure Parameters

Parameter	Description
name	Unique name used to identify the refresh group, specified as `[schema_name.]refresh_group_name`. If the schema is not specified, then the current user is the default. Refresh groups must follow the same naming conventions as tables.
list	Comma-delimited list of materialized views that you want to refresh. Synonyms are not supported. These materialized views can be located in different schemas and have different master tables or master materialized views. However, all of the listed materialized views must be in your current database. Each materialized view is specified as `[schema_name.]materialized_view_name`. If the schema is not specified, then the refresh group owner is the default.
tab	Instead of a comma-delimited list, you can supply a PL/SQL index-by table of names of materialized views that you want to refresh using the data type `DBMS_UTILITY`.`UNCL_ARRAY`. If the table contains the names of n materialized views, then the first materialized view should be in position 1 and the n + 1 position should be set to `NULL`. Each materialized view is specified as `[schema_name.]materialized_view_name`. If the schema is not specified, then the refresh group owner is the default.
next_date	Next date that you want a refresh to occur.
interval	Function used to calculate the next time to refresh the materialized views in the group. This field is used with the `next_date` value. For example, if you specify `NEXT_DAY(SYSDATE+1,` `"MONDAY")` as your interval, and if your `next_date` evaluates to Monday, then Oracle refreshes the materialized views every Monday. This interval is evaluated immediately before the refresh. Thus, you should select an interval that is greater than the time it takes to perform a refresh.
implicit_destroy	Set this to `TRUE` if you want to delete the refresh group automatically when it no longer contains any members. Oracle checks this flag only when you call the `SUBTRACT` procedure. That is, setting this flag still enables you to create an empty refresh group.
lax	A materialized view can belong to only one refresh group at a time. If you are moving a materialized view from an existing group to a new refresh group, then you must set this to `TRUE` to succeed. Oracle then automatically removes the materialized view from the other refresh group and updates its refresh interval to be that of its new group. Otherwise, the call to `MAKE` generates an error message.
job	Needed by the Import utility. Use the default value, 0.
rollback_seg	Name of the rollback segment to use while refreshing materialized views. The default, `NULL`, uses the default rollback segment.
push_deferred_rpc	Used by updatable materialized views only. Use the default value, `TRUE`, if you want to push changes from the materialized view to its associated master table or master materialized view before refreshing the materialized view. Otherwise, these changes might appear to be temporarily lost.
refresh_after_errors	Used by updatable materialized views only. Set this to 0 if you want the refresh to proceed even if there are outstanding conflicts logged in the `DEFERROR` view for the materialized view's master table or master materialized view.
purge_option	If you are using the parallel propagation mechanism (in other words, parallelism is set to 1 or greater), then 0 = do not purge; 1 = lazy (default); 2 = aggressive. In most cases, lazy purge is the optimal setting. Set purge to aggressive to trim back the queue if multiple master replication groups are pushed to different target sites, and updates to one or more replication groups are infrequent and infrequently pushed. If all replication groups are infrequently updated and pushed, then set purge to do not purge and occasionally execute `PUSH` with purge set to aggressive to reduce the queue.
parallelism	0 specifies serial propagation. n > 1 specifies parallel propagation with n parallel processes. 1 specifies parallel propagation using only one parallel process.
heap_size	Maximum number of transactions to be examined simultaneously for parallel propagation scheduling. Oracle automatically calculates the default setting for optimal performance. Note: Do not set this parameter unless directed to do so by Oracle Support Services.

REFRESH Procedure

This procedure manually refreshes a refresh group.

See Also:

Oracle Database Advanced Replication for more information about refresh groups

Syntax

DBMS_REFRESH.REFRESH (
   name   IN    VARCHAR2);

Parameter

Table 17-6 REFRESH Procedure Parameter

Parameter	Description
name	Name of the refresh group that you want to refresh manually.

SUBTRACT Procedure

This procedure removes materialized views from a refresh group.

See Also:

Oracle Database Advanced Replication for more information about refresh groups

Syntax

DBMS_REFRESH.SUBTRACT (
   name      IN    VARCHAR2,
   { list    IN    VARCHAR2,
   | tab     IN    DBMS_UTILITY.UNCL_ARRAY, }
   lax       IN    BOOLEAN := FALSE);

Note:

This procedure is overloaded. The list and tab parameters are mutually exclusive.

Parameters

Table 17-7 SUBTRACT Procedure Parameters

Parameter	Description
name	Name of the refresh group from which you want to remove members.
list	Comma-delimited list of materialized views that you want to remove from the refresh group. (Synonyms are not supported.) These materialized views can be located in different schemas and have different master tables or master materialized views. However, all of the listed materialized views must be in your current database.
tab	Instead of a comma-delimited list, you can supply a PL/SQL index-by table of names of materialized views that you want to refresh using the data type `DBMS_UTILITY`.`UNCL_ARRAY`. If the table contains the names of n materialized views, then the first materialized view should be in position 1 and the n + 1 position should be set to `NULL`.
lax	Set this to `FALSE` if you want Oracle to generate an error message if the materialized view you are attempting to remove is not a member of the refresh group.