The MAX_PDB_SNAPSHOTS database property sets the maximum number of snapshots for every PDB in a PDB snapshot carousel. The default maximum is 8. You cannot set the property to a number greater than 8.

Prerequisites

The PDB must be open in read/write mode.

To set the maximum number of PDB snapshots for a PDB:

1. In SQL*Plus, ensure that the current container is the PDB for which you want to set the limit.

2. Optionally, query CDB_PROPERTIES for the current setting of the SET MAX_PDB_SNAPSHOTS property.

3. Run an ALTER PLUGGABLE DATABASE or ALTER DATABASE statement with the SET MAX_PDB_SNAPSHOTS clause.

Prerequisites

Note the following prerequisites for the ALTER PLUGGABLE DATABASE SNAPSHOT statement:

• The CDB must be in local undo mode.

• The administrator must have the privileges to create a PDB and drop a PDB.

To configure automatic snapshots when altering a PDB:

1. In SQL*Plus, log in as an administrator to the PDB whose snapshot mode you intend to configure.

2. Optionally, query DBA_PDBS to determine the current snapshot mode.

3. Run ALTER PLUGGABLE DATABASE with the SNAPSHOT MODE EVERY interval clause, specifying either MINUTES or HOURS.

To configure automatic snapshots when creating a PDB:

1. In SQL*Plus, log in as an administrator to the CDB root or application root.

2. Optionally, query DBA_PDBS to determine the current snapshot mode.

3. Run CREATE PLUGGABLE DATABASE with the SNAPSHOT MODE EVERY interval clause, specifying either MINUTES or HOURS.

Prerequisites

Note the following prerequisites for the ALTER PLUGGABLE DATABASE SNAPSHOT statement:

• The CDB must be in local undo mode. You can check the mode by using the following query, which returns TRUE when local undo is enabled:

  SELECT * FROM DATABASE_PROPERTIES WHERE PROPERTY_NAME='LOCAL_UNDO_ENABLED';

• The DBA must have the privileges to create and drop a PDB.

• If you want the snapshots to be sparse, then the underlying storage system must support sparse files. In this case, only the first snapshot will be full.

To create a PDB snapshot:

1. In SQL*Plus, log in as an administrator to the PDB whose snapshot you intend to create.

2. Optionally, query DBA_PDBS.SNAPSHOT_MODE to confirm that the snapshot mode is not set to NONE.

3. Run an ALTER PLUGGABLE DATABASE statement with the SNAPSHOT clause.

To drop all PDB snapshots based on a PDB, set the MAX_PDB_SNAPSHOTS property in the PDB to 0 (zero).

To drop a PDB snapshot:

1. In SQL*Plus, ensure that the current container is the PDB from which you created the PDB snapshot.

2. Run an ALTER PLUGGABLE DATABASE statement with the DROP SNAPSHOT clause.

DBA_PDB_SNAPSHOTS contains general information about the snapshot, including name, SCN, time, and path. DBA_PDB_SNAPSHOTFILE shows the path and file type of every file in a snapshot: data files, archived redo log files, and XML files.

To view metadata for PDB snapshots:

1. In SQL*Plus, log in to the database as an administrative user.

2. Query DBA_PDB_SNAPSHOTS.

   For example, run the following query (sample output included):

   COL SNAPSHOT_NAME FORMAT a30
   SELECT SNAPSHOT_NAME, SNAPSHOT_SCN, SNAPSHOT_TIME FROM DBA_PDB_SNAPSHOTS;
   
   SNAPSHOT_NAME                  SNAPSHOT_SCN SNAPSHOT_TIME
   ------------------------------ ------------ -------------
   HRPDB_SNAP_F                        3678939    1536262569
   HRPDB_SNAP_S                        4954803     986473745

3. Query DBA_PDB_SNAPSHOTFILE.

   For example, run the following join query (sample output included):

   SET LINESIZE 120
   COL SNAPSHOT_NAME FORMAT a12
   COL SNAPSHOT_FILENAME FORMAT a54
   
   SELECT SNAPSHOT_NAME, SNAPSHOT_FILENAME, SNAPSHOT_FILETYPE AS TYPE
   FROM   DBA_PDB_SNAPSHOTS s, DBA_PDB_SNAPSHOTFILE f
   WHERE  s.SNAPSHOT_SCN=f.SNAPSHOT_SCN;
   
   SNAPSHOT_NAM SNAPSHOT_FILENAME                                      TYPE
   ------------ ------------------------------------------------------ ----
   HRPDB_SNAP_S /d1/snapshots/4954803/o1_mf_undo_1_fry1l5bq_.dbf       DATA
   HRPDB_SNAP_S /d1/snapshots/4954803/o1_mf_salestbs_fry19m6h_.dbf     DATA
   HRPDB_SNAP_S /d1/snapshots/4954803/o1_mf_sysext_fry19d1n_.dbf       DATA
   HRPDB_SNAP_S /d1/snapshots/4954803/o1_mf_sysaux_fry19d1m_.dbf       DATA
   HRPDB_SNAP_S /d1/snapshots/4954803/o1_mf_system_fry19d1k_.dbf       DATA
   HRPDB_SNAP_S /d1/snapshots/4954803/HRPDB.xml                         XML
   HRPDB_SNAP_S /d1/snapshots/4954803/archparlog_1_274_b87ca51e_985963
                814.arc                                                ARCH