Perform the following steps to create a PMEM filestore for an Oracle database:

1. Start the Oracle Database instance in NOMOUNT mode.
2. Execute the CREATE PMEM FILESTORE command to create the PMEM filestore and provide:
   • A mount point for the file store. The final subdirectory name must be the same as the PMEM filestore name.
   • A backing file from a native XFS or ext4 file system mounted in DAX mode.The backing file is used by the PMEM filestore to keep all the files created in the filestore.
   • A block size, which will typically be the same as the default block size of the database datafiles.
     As an example:

     CREATE PMEM FILESTORE db1_pmemfs
     MOUNTPOINT '/u1/db/db1_pmemfs'
     BACKINGFILE '/u1/db_storage/db1'
     SIZE 2T
     BLOCK SIZE 8K
     AUTOEXTEND ON NEXT 10G
     MAXSIZE 3T;

     The PMEM filestore is automatically mounted after it is created. The PMEM filestore will appear under the specified mount point as if it is a native file system.

3. Configure the PMEM filestore to be mounted during instance startup.

   If you used an SPFILE to start the database instance, the server adds the PMEM_FILESTORE initialization parameter to the SPFILE. This parameter causes the PMEM filestore to be automatically mounted when the database instance is started. The SPFILE will contain this entry following the execution of the CREATE PMEM FILESTORE command: PMEM_FILESTORE=(‘/u1/db/db1_pmemfs’, ‘/u1/db_storage/db1’). The first string in the parameter value list is the directory where the PMEM filestore is mounted. The second string is the backing file.

   If you did not use an SPFILE to start the database instance, you must manually add the PMEM_FILESTORE initialization parameter so that the PMEM filestore is mounted during instance startup. Or you must manually mount the PMEM filestore using the ALTER PMEM FILESTORE … MOUNT command.

After creating the PMEM filestore, you can use it as if it is a native file system to create an Oracle Database. You can create the database under the mount point you specified when you created the PMEM filestore. See Oracle Multitenant Administrator's Guide for detailed information.

After creating the PMEM filestore, perform the following steps to migrate an existing Oracle Database or select tablespaces to the PMEM filestore:

1. Copy the database files by using the RMAN RESTORE command or operating system commands.
2. Optionally, change the block size of the redo log files by creating new online redo log files and then dropping the existing redo log files.

You can also use the ALTER DATABASE command with the MOVE DATAFILE clause to move an online datafile to the PMEM filestore.

You can query V$PMEM_FILESTORE to view information about the PMEM filestore including:

• Directory path for the mount point of the PMEM filestore

• File path for the backing file of the PMEM filestore

• Block size of the PMEM filestore (in bytes)

• Current size of the PMEM filestore (in bytes)

• Whether it is autoextensible and details about the autoextensible configuration

• Space usage (free space and used space)

The following statement is used to mount the PMEM filestore:

• ALTER PMEM FILESTORE filestore_name MOUNT

If the initialization parameter file does not include the PMEM_FILESTORE parameter, you must include the MOUNTPOINT and BACKINGFILE clauses, along with the FORCE keyword when you execute this command.

You can also include the MOUNTPOINT and BACKINGFILE clauses with the FORCE keyword to specify different file paths than were specified in the intialization parameter file. If you used a server parameter file (SPFILE) to start the database instance, it will be updated with the file paths specified in the ALTER PMEM FILESTORE MOUNT command.

You must be connected to the root container (CDB$ROOT) as a user with the SYSDBA privilege to execute this command.

The following statement is used to dismount the PMEM filestore:

• ALTER PMEM FILESTORE filestore_name DISMOUNT

You must be connected to the root container (CDB$ROOT) as a user with the SYSDBA privilege to execute this command.

The following statement is used to change the attributes of the PMEM filestore:

• ALTER PMEM FILESTORE

If you want to change the mount point or backing file, you must first dismount the filestore. See Dismounting a PMEM Filestore.

You cannot change the block size of the filestore.

You must be connected to the root container (CDB$ROOT) as a user with the SYSDBA privilege to execute this command.

The following statement is used to drop the PMEM filestore:

• DROP PMEM FILESTORE

Specify INCLUDING CONTENTS to remove all of the files in the PMEM filestore. To drop the filestore immediately, use the FORCE keyword with INCLUDING CONTENTS. Specify EXCLUDING CONTENTS so that the PMEM filestore will be dropped only when it is empty.

If the database instance was started with an SPFILE, the SPFILE will be updated when DROP PMEM FILESTORE is executed.