Resolution:
In TIBCO iProcess Engine (iPE) prior to 11.3.0, participation records were not removed when their corresponding user was deleted. This lead to many orphaned participation records for deleted users. In iPE version 11.3.0, an enhancement was made for redirecting work items of deleted users. This change is documented in the Release Notes under "Redirect the Work Items of a Deleted User (IPE-2560)" in the following document:

https://docs.tibco.com/pub/iprocess-engine/11.3.0-november-2011/TIB_ipe_11.3.0_relnotes_oracle_unix.pdf

This change also removes participant records for users that are deleted from the iProcess Engine. 

There are two user maintenance scenarios that cause all users to be deleted and re-added into the iProcess Engine.

1). Performing a full swutil USERINFO import using a control file with an R at the top.
2). Performing the first full LDAP sync after changing from a STAFFWARE DIT to an LDAP DIT.

Both of the above activities will remove and re-add all users to the iProcess Engine. During this activity, all participation records for those users are also deleted. To preserve existing participation records during these activities, users should first export all participation records using the swutil PARTICIPATION command and then re-import the participation information after your user maintenance is complete. Use of the swutil PARTICIPATION command is documented at the following:

https://docs.tibco.com/pub/iprocess-engine/11.3.0-november-2011/pdf/tib-iprocess-swutil-swbatch-reference.pdf

After upgrading the TIBCO iProcess Engine from a version prior to 11.3.0, you may notice circumstances when all participation records are removed.

https://docs.tibco.com/pub/iprocess-engine/11.3.0-november-2011/TIB_ipe_11.3.0_relnotes_oracle_unix.pdf
https://docs.tibco.com/pub/iprocess-engine/11.3.0-november-2011/pdf/tib-iprocess-swutil-swbatch-reference.pdf