Home > Workload Solutions > Oracle > White Papers > Dell PowerMax 2500 and 8500 Best Practices for Mission Critical Oracle Databases > Appendix 3. AFD online storage reclamation example
The following example illustrates the value of AFD online storage reclamation. It is performed using PowerMax 8500, Oracle database, and GI 19c with AFD running in an Oracle Linux 8.5 server.
Start with an empty ASM disk group called +THIN and a matching PowerMax SG called OraAFD_Thin. In a real customer environment, the ASM disk group will not be empty.
Enable thin provisioning attribute for the ASM disk group.
SQL> ALTER DISKGROUP THIN SET ATTRIBUTE 'THIN_PROVISIONED'='TRUE';
Diskgroup altered.
SQL> select dg.name, attr.name, attr.value from v$asm_diskgroup dg, v$asm_attribute attr where dg.group_number=attr.group_number and attr.name='thin_provisioned';
NAME NAME VALUE
------------- ---------------------- ---------------
DB thin_provisioned FALSE
GRID thin_provisioned FALSE
THIN thin_provisioned TRUE
The SG capacity of the empty ASM disk group shows that ASM is efficient with metadata and only consumes 0.1 GB of actual storage capacity.
symcfg -sid 304 list -tdev -sg OraAFD_Thin_SG -gb
S Y M M E T R I X T H I N D E V I C E S
-----------------------------------------------
Effective Data
Flgs Provisioned Used Reduction
Sym EMPT GBs GBs (%) Ratio
----- ---- ----------- ---------- --- ---------
001C8 F... 40.0 0.0 0 -
001C9 F... 40.0 0.0 0 -
001CB F... 40.0 0.0 0 -
Total ----------- ---------- --- ---------
GBs 120.0 0.1 0
Next, a tablespace of a 100 GB is created and then dropped in the ASM disk group. When Oracle creates a tablespace with its datafiles, it initializes the space. As a result, a 100 GB of storage capacity is consumed.
SQL> CREATE BIGFILE TABLESPACE TP1 DATAFILE '+THIN' size 100G ONLINE;
Tablespace created.
SQL> DROP TABLESPACE TP1 INCLUDING CONTENTS AND DATAFILES;
Tablespace dropped.
After the tablespace is created and the capacity consumed in the storage, it is not automatically released when the tablespace is dropped, as shown in the following output.
symcfg -sid 304 list -tdev -sg OraAFD_Thin_SG -gb
S Y M M E T R I X T H I N D E V I C E S
-----------------------------------------------
Effective Data
Flgs Provisioned Used Reduction
Sym EMPT GBs GBs (%) Ratio
----- ---- ----------- ---------- --- ---------
001C8 F... 40.0 33.4 83 -
001C9 F... 40.0 33.4 83 -
001CB F... 40.0 33.4 83 -
Total ----------- ---------- --- ---------
GBs 120.0 100.1 0
To achieve the online storage reclamation, rebalance the ASM disk group.
SQL> ALTER DISKGROUP THIN REBALANCE WAIT;
Diskgroup altered.
The Solutions Enabler CLI output confirms that the 100 GB capacity was reclaimed.
symcfg -sid 304 list -tdev -sg OraAFD_Thin_SG -gb
S Y M M E T R I X T H I N D E V I C E S
-----------------------------------------------
Effective Data
Flgs Provisioned Used Reduction
Sym EMPT GBs GBs (%) Ratio
----- ---- ----------- ---------- --- ---------
001C8 F... 40.0 0.0 0 -
001C9 F... 40.0 0.0 0 -
001CB F... 40.0 0.0 0 -
Total ----------- ---------- --- ---------
GBs 120.0 0.1 0