Oracle Built−in Packages- P127 doc

group In this example, we create a snapshot refresh group of read−only snapshots: DECLARE vSnapshotList dbms_utility.uncl_array BEGIN vSnapshotList1 = 'COUNTRIES' vSnapshotList2 = 'STA

Trang 1

(Oracle8 only)

Used only if parallelism > 0 Sets the maximum number of transactions to be examined simultaneously for determining parallel scheduling Oracle determines this value internally; you are advised not to use it

The MAKE procedure does not raise any exceptions

14.2.2.1.1 Examples

The following examples illustrate how the MAKE procedure may be used

14.2.2.1.2 Read−only snapshot group

In this example, we create a snapshot refresh group of read−only snapshots:

DECLARE

vSnapshotList dbms_utility.uncl_array

BEGIN

vSnapshotList(1) = 'COUNTRIES'

vSnapshotList(2) = 'STATES'

vSnapshotList(3) = 'POSTAL_CODES'

vSnapshotList(4) = 'CUSTOMER_ADDRESSES'

DBMS_REFRESH.MAKE(name => 'SG_ADDR_TABS',

tab => vSnapShotList,

next_date => TRUNC(sysdate) + 1,

interval => 'SYSDATE + 1');

END;

This example shows the simplest invocation of DBMS_REFRESH.MAKE; defaults are used for all possible parameters This call creates a snapshot group on four related tables, and schedules them to be refreshed at every day at midnight

14.2.2.1.3 Read−only snapshot group with specialized parameters

In the following example, we create a snapshot refresh group of read−only snapshots with specialized

parameters:

DECLARE

BEGIN

interval => 'SYSDATE + 1',

implicit_destroy => TRUE,

lax => TRUE,

rollback_segment 'RB1');

END;

This example creates the same snapshot group as in the previous example, but with some additional

properties:

implicit_destroy = TRUE

This setting causes the snapshot group SG_ADDR_TABS to be destroyed if all of the snapshots in the group are dropped The default behavior is to preserve the snapshot group, even if it has no members

14.2.2 Creating and Destroying Snapshot Groups 621

Trang 2

lax = TRUE

If any of the snapshots being added to SG_ADDR_TABS exist in another snapshot group, this setting instructs Oracle to remove them from the other group before adding them to the new group A

snapshot cannot be a member of more than one snapshot group

rollback_segment = `RB1'

This setting causes Oracle to use rollback segment RB1 whenever it refreshes snapshot group

SG_ADDR_TABS You should consider specifying rollback segments if your snapshot refreshes result in long transactions requiring a large rollback segment

14.2.2.1.4 Parallel propagation

In the next example, we create a snapshot refresh group that uses parallel propagation (Oracle8 only):

DECLARE

BEGIN

interval => 'SYSDATE + 1',

parallelism => 4,);

END;

This example sets parallelism to 4, so that Oracle uses four processes to perform the refresh

14.2.2.2 The DBMS_REFRESH.DESTROY procedure

Call the DESTROY procedure to destroy a snapshot group For both Oracle7 and Oracle8, you call

DESTROY as follows,

PROCEDURE DBMS_REFRESH.DESTROY (name IN VARCHAR2);

where name is the name of the snapshot group to be destroyed

The DESTROY procedure raises the following exception:

Name Number Description

ORA−23404 −23404 Refresh group name does not exist

14.2.2.2.1 Example

This example destroys the snapshot group SG_ADDR_TABS:

BEGIN

DBMS_REFRESH.DESTROY( name => 'SG_ADDR_TABS' );

END;

This example does not drop the member snapshots themselves; however, they will not be refreshed again unless you either add them to another snapshot group, or refresh them manually with the

DBMS_SNAPSHOT.REFRESH procedure

14.2.2 Creating and Destroying Snapshot Groups 622

Trang 3

14.2.3 Adding and Subtracting Snapshots from Snapshot Groups

With the ADD and SUBTRACT procedures, you can add and subtract the snapshots in a snapshot group after you have created the group As with the other DBMS_REFRESH procedures, you must call these procedures from the snapshot site

NOTE: A snapshot group cannot have more than 100 members.

14.2.3.1 The DBMS_REFRESH.ADD procedure

Call the ADD procedure to add a snapshot group The specification follows:

PROCEDURE DBMS_REFRESH.ADD

(name IN VARCHAR2,

{list IN VARCHAR2,| tab IN dbms_utility.uncl_array,}

lax IN BOOLEAN DEFAULT FALSE );

The parameters for the ADD procedure have the same meaning as in the MAKE procedure; refer to the parameter table in that section Note that you must select the list or tab parameter, but not both

The ADD procedure does not raise any exceptions

14.2.3.1.1 Example

This example uses the ADD procedure to add the snapshots PROVINCES and CONTINENTS to the existing snapshot group SG_ARR_TABS:

BEGIN

DBMS_REFRESH.ADD

(name => 'SG_ADDR_TABS', list => 'PROVINCES', CONTINENTS');

END;

14.2.3.2 The DBMS_REFRESH.SUBTRACT procedure

Call the SUBTRACT procedure to subtract a snapshot group The specification follows:

PROCEDURE DBMS_REFRESH.SUBTRACT

(name IN VARCHAR2,

{list IN VARCHAR2,| tab IN dbms_utility.uncl_array,}

lax IN BOOLEAN DEFAULT FALSE );

The parameters for the SUBTRACT procedure have the same meaning as in the MAKE procedure; refer to the parameter table in that section Note that you must select the list or tab parameter, but not both

The SUBTRACT procedure does not raise any exceptions

14.2.3.2.1 Example

The following example removes the snapshots STATES and COUNTRIES from the existing snapshot group SG_ADDR_TABS Since we also specified lax = TRUE, the call also drops the snapshot group if there are no other member snapshots remaining

BEGIN

DBMS_REFRESH.SUBTRACT( name => 'SG_ADDR_TABS',

list => 'STATES', COUNTRIES',

lax => TRUE);

END;

14.2.3 Adding and Subtracting Snapshots from Snapshot Groups 623

Trang 4

14.2.4 Altering Properties of a Snapshot Group

The CHANGE procedure allows you to modify settings associated with a snapshot group You can change any of the parameters that are available in DBMS_REFRESH.MAKE:

interval

implicit_destroy

rollback_segment

push_deferred_rpc

refresh_after_errors

purge_option (Oracle8 only)

parallelism (Oracle8 only)

heap_size (Oracle8 only)

Refer to the MAKE section for an explanation of these parameters

14.2.4.1 The DBMS_REFRESH.CHANGE procedure

Call the CHANGE procedure to modify a snapshot group's setting The specifications for CHANGE differ for Oracle7 and Oracle8 as follows

Here is the Oracle7 specification:

PROCEDURE DBMS_REFRESH.CHANGE

(name IN VARCHAR2,

next_date IN DATE DEFAULT NULL,

interval IN VARCHAR2 DEFAULT NULL,

implicit_destroy IN BOOLEAN DEFAULT NULL,

rollback_seg IN VARCHAR2 DEFAULT NULL,

push_deferred_rpc IN BOOLEAN DEFAULT NULL,

refresh_after_errors IN BOOLEAN DEFAULT NULL);

Here is the Oracle8 specification:

PROCEDURE 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);

As with the MAKE procedure, the difference between the Oracle7 and Oracle8 CHANGE specifications is the inclusion of support for parallel propagation and purging in the Oracle8 version

The CHANGE procedure does not raise any exceptions

14.2.5 Manually Refreshing Snapshot Groups

The REFRESH procedure refreshes a snapshot group

14.2.4 Altering Properties of a Snapshot Group 624

Trang 5

14.2.5.1 The DBMS_REFRESH.REFRESH procedure

Call REFRESH to refresh a snapshot group A call to REFRESH causes all members of snapshot group name

to be refreshed with the settings that you have designated in DBMS_REFRESH.MAKE and/or

DBMS_REFRESH.CHANGE The specification is,

PROCEDURE DBMS_REFRESH.REFRESH (name IN VARCHAR2);

where name identifies the snapshot group

The REFRESH procedure does not raise any exceptions

14.1 DBMS_SNAPSHOT:

Managing Snapshots

14.3 DBMS_OFFLINE_SNAPSHOT:

Performing Offline Snapshot

Instantiation

14.2.5 Manually Refreshing Snapshot Groups 625

Định dạng
Số trang	5
Dung lượng	86,05 KB