What causes could lead to a hung SAP HANA database where blocking transactions cannot be identified?

A long savepoint duration can indeed lead to a hung SAP HANA database where blocking transactions cannot be identified. This phenomenon occurs because during a savepoint, the system must write changes from memory to disk. If the savepoint operation takes an excessively long time, it can result in the database being unable to process other transactions, thus leading to a state where the database appears to be hung. Longer savepoints can also contribute to increased transaction wait times if there are concurrent transactions that need to acquire locks on database resources that are currently being held.

When savepoints take too long due to heavy data writes or other resource contention, it can effectively block other processes that depend on the database to function correctly, creating a situation where blocking transactions are not easily identifiable since the system is under stress from the ongoing savepoint operation. This is particularly critical in high-performance environments where speed and responsiveness are key to operational success.

Other potential causes, while they may contribute to performance issues, do not directly result in the same kind of behavior relative to transaction blocking. For instance, excessive memory allocation can lead to performance degradation but does not necessarily cause transactions to be stuck. A restriction on CPU usage might throttle performance but does not inherently create a blockage within the transaction processing. Likewise,