Detail:
The system archivine all data except runtime data that belongs to work item.Once archived data
can only be used to display and cannot be reloaded to table again.You can only archive completed workflow items and its dependent.Along with it you can archive log data,workflow manager data and work item attachment.
Workitem that can be archive that have following statues.
Completed (Executon of Workitem Completed)
Logically Deleted (Cancelled item no longer useful)
Your SAP work flow and its related tables are SWZAIRET,SWZAIENTRY,SWZAI,SWWWIRET,SWWWIHEAD,SWWWIDEADL,SWWWIAGENT,SWWLOGPARA,SWWLOGHIST,SWWEI,SWWCNTPADD,SWWCNTP0,SWW_WI2OBJ,SWW_CONTOB,SWW_CONT,SWPSTEPLOG,SWPNODELOG,SWPNODE,SWPCMPCONT,SWP_NODEWI,SWP_JOIN,SWP_HEADER,SWFGPROLEINST
Procedure :
Step 1:
1. Create the Content Repository in Tcode: Oac0 and Save
Step 2:
1. Run Tcode : SARA with Archiving object WORKITEM.

2. Click on Customizing to perform Archiving Object Specific Customization.
3. Click on Technical Setting for Further Configuration and configure accordingly to your requirement.In this I have not choosen the option to start the job to move the archiving to content server and delete the archive file.
Step 3:
1. Check the no. of entries available of SWWWIHEAD have status Completed / Cancelled by specifying the date.
2. Run Tcode : SARA with Archiving object WORKITEM.
3. Write the Workflow to Archive
4. Now Create the Write Variant and click Edit.
5. Select for all Selection Screen and Provide the Workflow creation date and provide the description under attribute and SAVE.
6. Maintain the Job execution date and and spool parameter and execute.
7. Monitor the Archiving Write Job from SM37.
8. After sucessful Job finish, Click on Storage System , then Archive Files.
9. Select the session files and Job Start date and time and Execute it as background.
10. Store Trigger Job can be monitor from SM37
11. After the Job is finished , we can run the delete for the that created archive session.
12. Selcet the Session Files, set the job scedule and spool parameter and execute.
13. Monitor the deletion job from SM37.
To read the archive data of the session it can be either done with GOS menu or from tcode SARI --> Archive Explorer --> Archiving Object -"WORKITEM" , Archive Infostructure - "SAP_O_2_WI_001".