4.245 DBA_EXTERNAL_SCN_ACTIVITY
DBA_EXTERNAL_SCN_ACTIVITY
works in conjunction with the DBA_DB_LINK_SOURCES
and DBA_DB_LINKS
views to determine the source of high SCN activities.
If the SCN is increased by an inbound database link, then you can join the DBA_EXTERNAL_SCN_ACTIVITY
view with the DBA_DB_LINK_SOURCES
view on the INBOUND_DB_LINK_SOURCE_ID
column to get details of the remote database where the SCN increase originated.
If the SCN is increased by an outbound database link, then the INBOUND_DB_LINK_SOURCE_ID
column will be NULL
, but the OUTBOUND_DB_LINK_NAME
and OUTBOUND_DB_LINK_OWNER
columns can be joined with the DB_LINK
and OWNER
columns respectively in the DBA_DB_LINKS
view to determine the remote database that caused the SCN increase.
If neither of the above cases are true (the INBOUND_DB_LINK_SOURCE_ID
, OUTBOUND_DB_LINK_NAME
, and OUTBOUND_DB_LINK_OWNER
are all NULL
), then the SCN increase resulted from a client connection and not as a result of a database link to or from another database. You can join the SESSION_ID
and SESSION_SERIAL#
columns with the SID
and SERIAL#
columns in V$SESSION
to get the client session details.
In a multitenant container database (CDB) environment, for every DBA_ view, there is a corresponding CDB_ view that contains data for all the pluggable databases (PDBs) in the CDB.
As the SCN is a property of the CDB (and not a PDB), a DBA interested in understanding large SCN jumps will likely find the CDB_EXTERNAL_SCN_ACTIVITY
view more useful for diagnosing SCN jumps on a CDB. Querying the CDB_EXTERNAL_SCN_ACTIVITY
view from CDB$ROOT
ensures that external SCN jumps occurring on all PDBs are looked at and noticed. On the other hand, a query on the corresponding DBA_EXTERNAL_SCN_ACTIVITY
view, or a query on the CDB_EXTERNAL_SCN_ACTIVITY
view done from a PDB would only show data for that PDB (that is, details regarding any external activity that occurred on that specific PDB that resulted in large SCN jumps).
Note that the CDB_ views would only show data from PDBs that are open at the time the query is issued. Therefore, when you are diagnosing sources of external SCN activities, Oracle recommends that you keep open any or all PDBs that might contain useful information for the diagnosis.
Column | Datatype | NULL | Description |
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Timestamp when SCN was received in UTC |
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Session identifier of the local session that created this entry. Maps to |
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Session serial number of the local session that created this entry. Maps to |
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Session identifier that can be joined with |
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Oracle username of the user who logged into the local database. Maps to |
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If the SCN was bumped by an inbound database link, then this is the inbound database link identified by the If the SCN was not increased by an inbound database link, then this value is null. |
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If the SCN was bumped by an outbound database link, then this is the outbound database link identified by the Using this column and the If the SCN was not increased by an outbound database link, then this value is null. |
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If the SCN was bumped by an outbound database link, then this is the owner of the outbound database link identified by Using this column and the If the SCN was not increased by an outbound database link, then this value is null. |
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The following SCN activities are captured:
Regular SCN activities which do not result in errors or warnings are not captured . SCN errors and warnings also appear in |
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The external SCN received from an inbound database link, an outbound database link, or a client |
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For For |
See Also: