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How to reduce the Highwater of LOGMNR_RESTART_CKPT$ (Doc ID 429599.1) To BottomTo Bottom

In this Document
Goal
Solution
APPLIES TO:
Oracle Database - Enterprise Edition - Version 10.2.0.2 to 11.2.0.2.0 [Release 10.2 to 11.2]
Oracle Database Cloud Schema Service - Version N/A and later
Oracle Database Exadata Express Cloud Service - Version N/A and later
Oracle Database Exadata Cloud Machine - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Information in this document applies to any platform.
GOAL
Oracle Streams enables the sharing of data and events in a data stream, either within a database or from one database to another. This article is intended to provide information regarding the management of LOGMNR_RESTART_CKPT$ table.

SOLUTION
Periodically, the mining process checkpoints itself for quicker restart.
These checkpoint information is maintained in the SYSAUX tablespace by default.

From Oracle 10.2 onwards, the purging of logmnr_restart_ckpt$ is done automatically
by Oracle. There is a capture parameter checkpoint_retention_time that determines how
frequently the purge occurs.

CHECKPOINT_RETENTION_TIME, controls the amount of checkpoint data that is retained by
moving the FIRST_SCN of the capture process forward. When the checkpoint_retention_time
is exceeded (default = 60 days), the FIRST_SCN is moved and the Streams metadata tables
previous to this scn(FIRST_SCN) can be purged. Space in the SYSAUX tablespace should be
reclaimed at this time.

You can alter checkpoint_retention_time to lesser value to purge the metatdata
tables more frequently using the following syntax :

exec dbms_capture_adm.alter_capture(capture_name =>’ ',CHECKPOINT_RETENTION_TIME=>);

For example :-

exec dbms_capture_adm.alter_capture(capture_name =>'STRMADMIN_CAPTURE ',CHECKPOINT_RETENTION_TIME=>7);

Here we are setting the retention time to 7 days. Any data in table logmnr_restart_ckpt$
older than 7 days is purged automatically.

You can then use the shrink command to manually free unused space both above and
below the high water mark of the table.

alter table system.LOGMNR_RESTART_CKPT$ enable row movement;
alter table system.LOGMNR_RESTART_CKPT$ shrink space ;
alter table system.LOGMNR_RESTART_CKPT$ disable row movement;

The index associated with the table can be shrunk using

alter index shrink space;

NOTE: When we alter these objects, it may leave some Streams related packages and views in SYS invalid.

To validate these invalid objects you need to run the utlrp package

SQL> @?/rdbms/admin/utlrp.sql

It is also useful to tune _checkpoint_frequency appropriately in order to minimise the checkpoint information stored and this should be mentioned.

If we minimise the amount of data stored then it will optimise any shrink that needs to be performed.