Estimated space for Compliance Window on RA

 In this post  I will go through how to estimate how much space you need to store backups on the Recovery Appliance to meet your Compliance Window.

This is critical to understand, since compliance protected backups cannot be removed from the RA, and if all space is utilized to meet Compliance Windows, new backups will be refused.

First a bit about Compliance window.

COMPLIANCE WINDOW

Compliance Window is set at the Policy level.  All databases within that policy will inherit the Compliance Window going forward.  Below is some more detail you need to know on Compliance Window.

• The Compliance Window cannot be greater than the Recovery Window Goal
• You cannot set the Policy to "Auto Tune" reserve space when setting a Compliance Window. You must manage the reserve space as you did in the past.
• The Compliance Window can be adjusted up or down once set, but this will not affect any previous backups. Backups previously created observe the Compliance Window in effect when the backup was created.
• The RA does not have to be in Compliance Mode (disabled direct root access) in order to set the a Compliance Window.

Space management for Compliance Window

Reserved Space

If you are familiar with reserved space, then you understand how that can help.  Reserved space is set for each database, and is the estimate of how much is needed to meet the Recovery Window Goal.  The major points to understand with reserved space are

• The sum of all reserved space cannot be greater than the usable space on the RA.
• Reserved space is used during space pressure to determine which databases will not be able to keep their recovery window goal. Databases with reserved space less than what is needed will have their older backups purged first.
• Reserved space should be either
• About 10% greater than the space needed to meet the recovery window goal
• The high water mark of space needed during large volume updates (Black Friday sales for example).

By setting the reserved space for each database to be 10% larger than the space needed to meet the recovery window goal, you can alert when the Recovery Appliance cannot accept new databases to be backed up.  If all reserved space is allocated, then the Recovery Appliance is 90% full.

Recovery Window Goal

Within each policy you set a recovery window goal. This is a "goal" and if you run into space pressure, backups can be deleted from databases with insufficient reserved space (noted in the previous section).

The recommendation is to set the Compliance Window smaller than Recovery Window Goal if all databases are being protected.

By setting the recovery window goal smaller, you can alert when the required space to meet the recovery window goal is not available on the Recovery Appliance.  This will give you time to determine the space issue and take corrective action.

Compliance Window

Within each policy you can set a Compliance Window. This will lock any backups for the protected databases from being deleted, and will disable the database from being from the Recovery Appliance as long as it has backups that fall under compliance.  Since these backups cannot be removed, and the database cannot be removed, it is critical that you do not reach the point where all storage is utilized by compliant backups.

ESTIMATING COMPLIANCE SPACE

As you can tell by reading through how this works, it is critical to understand the space needed for compliant backups. 

The recommendation to estimate the space needed is to utilize the DBMS_RA.ESTIMATE_SPACE package.

Unfortunately with release 21.1 you cannot call this package from within a SQL statement. You will receive the following error.

Select dbms_ra.estimate_space ('TIMSP' , numtodsinterval(45,'day')) from dual
       *
ERROR at line 1:
ORA-14551: cannot perform a DML operation inside a query
ORA-06512: at "RASYS.DBMS_RA_MISC", line 5092
ORA-06512: at "RASYS.DBMS_RA", line 1204
ORA-06512: at line 1

In order to help everyone calculate the space needed, I came up with a code snippet that can give you the data you need.

Using the snippet below, and setting the variable for compliance window you can create an HTML report that will show you the estimate for space needed.

SET SERVEROUTPUT ON DECLARE x NUMBER; v_POLICY_NAME varchar2(128) := 'empty policy'; v_disk_reserved_space number :=0; v_size_estimate number :=0; v_compliance_window_space number := 0; v_recovery_window_space number :=0; vt_disk_reserved_space number :=0; vt_size_estimate number :=0; vt_recovery_window_space number :=0; vt_compliance_window_space number := 0; /*******************************************************/ /*******************************************************/ /*******************************************************/ /*******************************************************/ /* set the compliance window below */ /*******************************************************/ /*******************************************************/ /*******************************************************/ /*******************************************************/ V_COMPLIANCE_WINDOW_ESTIMATE DSINTERVAL_UNCONSTRAINED := numtodsinterval(15,'DAY'); BEGIN dbms_output.put_line('<HTML>'); dbms_output.put_line('<HEAD>'); dbms_output.put_line('<style>'); dbms_output.put_line('table {'); dbms_output.put_line('border: 1px solid #666;'); dbms_output.put_line('table-layout: fixed;'); dbms_output.put_line('width: 220px;'); dbms_output.put_line('}'); dbms_output.put_line('th,'); dbms_output.put_line('td {'); dbms_output.put_line('border: 1px solid #666;'); dbms_output.put_line('width: 140px;'); dbms_output.put_line('overflow: hidden;'); dbms_output.put_line('}'); dbms_output.put_line('</style>'); dbms_output.put_line('</HEAD>'); dbms_output.put_line('<BODY>'); dbms_output.put_line('<TABLE>'); dbms_output.put_line('<caption> Compliance Window of ' || extract(day from V_COMPLIANCE_WINDOW_ESTIMATE) || ' days sizing data for all database </caption>'); dbms_output.put_line('<colgroup>'); dbms_output.put_line('<col span="2">'); dbms_output.put_line('<col style="border: 2px solid black">'); dbms_output.put_line('<col span="7">'); dbms_output.put_line('</colgroup>'); dbms_output.put_line('<TR>'); dbms_output.put_line('<TH>'||'Policy'||' </TH> '); dbms_output.put_line('<TH>'||'Database Name'||' </TH> '); dbms_output.put_line('<TH>'||'Database Size'||' </TH> '); dbms_output.put_line('<TH>'||'Recovery Window Goal'||' </TH> '); dbms_output.put_line('<TH>'||'Reserved Space'||' </TH> '); dbms_output.put_line('<TH>'||'RWG Space'||' </TH> '); dbms_output.put_line('<TH>'||'Compliance space'||' </TH> '); dbms_output.put_line('</TR>'); dbms_output.put_line('</TABLE>'); FOR item IN (Select db_unique_name, POLICY_NAME, recovery_window_goal, disk_reserved_space , size_estimate, recovery_window_space from rasys.ra_database order by policy_name,db_unique_name) LOOP x := dbms_ra.estimate_space(db_unique_name => item.db_unique_name, target_window => V_COMPLIANCE_WINDOW_ESTIMATE ); if item.policy_name != v_policy_name THEN if v_policy_name != 'empty policy' then dbms_output.put_line('<TABLE>'); dbms_output.put_line('<TD>'||v_policy_name ||' Total </TD> '); dbms_output.put_line('<TD>'||' ' ||' </TD> '); dbms_output.put_line('<TD>'||to_char(v_size_estimate,'9,999,999') ||' GB </TD> '); dbms_output.put_line('<TD>'||' ' ||' </TD> '); dbms_output.put_line('<TD>'||to_char(v_disk_reserved_space,'9,999,999') ||' GB </TD> '); dbms_output.put_line('<TD>'||to_char(v_recovery_window_space,'9,999,999') ||' GB </TD> '); dbms_output.put_line('<TD>'||to_char(v_compliance_window_space,'9,999,999') ||' GB </TD> '); dbms_output.put_line('</TABLE>'); end if; dbms_output.put_line('<TABLE>'); dbms_output.put_line('<TD>'||item.policy_name ||' </TD> '); dbms_output.put_line('<TD>'||' ' ||' </TD> '); dbms_output.put_line('<TD>'||' ' ||' </TD> '); dbms_output.put_line('<TD>'||' ' ||' </TD> '); dbms_output.put_line('<TD>'||' ' ||' </TD> '); dbms_output.put_line('<TD>'||' ' ||' </TD> '); dbms_output.put_line('<TD>'||' ' ||' </TD> '); dbms_output.put_line('</TABLE>'); end if; dbms_output.put_line('<TABLE>'); if item.policy_name <> v_policy_name THEN v_disk_reserved_space := item.disk_reserved_space ; v_size_estimate := item.size_estimate; v_recovery_window_space := item.recovery_window_space; v_compliance_window_space := x; v_policy_name := item.policy_name; else v_disk_reserved_space := v_disk_reserved_space + item.disk_reserved_space; v_size_estimate := v_size_estimate + item.size_estimate; v_recovery_window_space := v_recovery_window_space + item.recovery_window_space; v_compliance_window_space := v_compliance_window_space + x; end if; dbms_output.put_line('<TD>'||' ' ||' </TD> '); vt_disk_reserved_space := vt_disk_reserved_space + item.disk_reserved_space; vt_size_estimate := vt_size_estimate + item.size_estimate; vt_recovery_window_space := vt_recovery_window_space + item.recovery_window_space; vt_compliance_window_space := vt_compliance_window_space + x; dbms_output.put_line('<TD>'||item.db_unique_name ||' </TD> '); dbms_output.put_line('<TD>'||to_char(item.size_estimate,'999,999') ||' GB </TD> '); dbms_output.put_line('<TD>'||extract(day from item.recovery_window_goal) ||' </TD> '); dbms_output.put_line('<TD>'||to_char(item.disk_reserved_space,'999,999') ||' GB </TD> '); dbms_output.put_line('<TD>'||to_char(item.recovery_window_space,'999,999')||' GB </TD> '); dbms_output.put_line('<TD>'||to_char(x,'999,999') ||' GB </TD> '); dbms_output.put_line('</TABLE>'); END LOOP; dbms_output.put_line('<TABLE>'); dbms_output.put_line('<TD>'||v_policy_name ||' Total </TD> '); dbms_output.put_line('<TD>'||' ' ||' </TD> '); dbms_output.put_line('<TD>'||to_char(v_size_estimate,'9,999,999') ||' GB </TD> '); dbms_output.put_line('<TD>'||' ' ||' </TD> '); dbms_output.put_line('<TD>'||to_char(v_disk_reserved_space,'9,999,999') ||' GB </TD> '); dbms_output.put_line('<TD>'||to_char(v_recovery_window_space,'9,999,999') ||' GB </TD> '); dbms_output.put_line('<TD>'||to_char(v_compliance_window_space,'9,999,999') ||' GB </TD> '); dbms_output.put_line('</TABLE>'); dbms_output.put_line('<TABLE>'); dbms_output.put_line('<TD>'|| '' ||'Grand Total </TD> '); dbms_output.put_line('<TD>'||' ' ||' </TD> '); dbms_output.put_line('<TD>'||to_char(vt_size_estimate,'9,999,999') ||' GB </TD> '); dbms_output.put_line('<TD>'||' ' ||' </TD> '); dbms_output.put_line('<TD>'||to_char(vt_disk_reserved_space,'9,999,999') ||' GB </TD> '); dbms_output.put_line('<TD>'||to_char(vt_recovery_window_space,'9,999,999') ||' GB </TD> '); dbms_output.put_line('<TD>'||to_char(vt_compliance_window_space,'9,999,999') ||' GB </TD> '); dbms_output.put_line('</TABLE>'); dbms_output.put_line('</BODY>'); dbms_output.put_line('</HTML>'); END; /

What the output looks like is below.  Note you can adjust the compliance window you want to look at.

This should allow you to look at the effect of setting a compliance window and compare it to the reserved space, and the RWG database by database, policy by policy, and as a whole.