HiRDB provides the following five lock modes for each type of locked resource (such as table or page):

1. Shared mode (PR: Protected Retrieve)
   One transaction monopolizes the locked resource and allows only referencing by other transactions.
   
2. Exclusive mode (EX: EXclusive)
   One transaction monopolizes the locked resource and does not allow referencing, adding, updating, or deletion by other transactions.
   
3. Shared retrieval mode (SR: Shared Retrieve)
   If the lock is applied to a certain resource in the shared mode, the shared retrieval mode applies to the resources above that locked resource; referencing, adding, updating, and deletion of the locked resource can be performed by other transactions.
   
4. Shared update mode (SU: Shared Update)
   If the lock is applied to a certain resource in the exclusive mode, the shared update mode applies to the resources above that locked resource; referencing, adding, updating, and deletion can be performed by other transactions.
   
5. Protected update mode (PU: Protected Update)
   Referencing, adding, updating, and deletion can be performed; referencing only can be performed by other transactions. Unlike modes 1-4, this mode occurs as a result of lock mode transition.