Error
Error Code:
1346
SAP S/4HANA Error 1346: Concurrent Read/Write Conflict
Description
This error indicates that a database operation attempted to perform both read and write actions on the same data concurrently, which is disallowed to maintain data integrity and consistency. It typically arises in scenarios involving SQLScript procedures or complex views where a statement tries to modify data that is also being read within the same transactional context.
Error Message
ERR_SQLSCRIPT_NOT_ALLOWED_CONCURRENT_READ_AND_WRITE: Not allowed concurrent read and write
Known Causes
3 known causesSQLScript Design Flaw
A SQLScript procedure or function is designed in a way that attempts to read and write to the same table or data set within a single, atomic operation, violating concurrency rules.
Complex View Logic
A complex view or calculation view might implicitly trigger concurrent read/write operations when underlying tables are accessed for both retrieval and update within the same execution path.
Incorrect Transactional Scope
The database transaction is not properly managed, leading to a situation where a statement tries to modify data that is already being read by another part of the same transaction or a closely related concurrent operation.
Solutions
3 solutions available1. Optimize Database Transactions and Locking Mechanisms advanced
Review and tune application logic to minimize the duration of write locks and ensure reads don't conflict with writes.
1
Analyze application code for long-running transactions that hold write locks on critical tables. Identify specific ABAP programs or function modules involved in the conflicting operations.
2
Utilize SAP's performance analysis tools (e.g., ST05, SAT, STAD) to pinpoint the exact SQL statements causing the contention. Focus on statements that are executed concurrently and access the same data.
3
Refactor application logic to reduce the scope of write operations. If possible, break down large transactions into smaller, independent units of work. This minimizes the time locks are held.
4
Review the use of pessimistic locking (e.g., `ENQUEUE` operations in ABAP) and consider more optimistic approaches if appropriate, or ensure locks are released promptly after use.
5
For critical read operations that might conflict with writes, consider using read-committed isolation levels or snapshot isolation if supported and appropriate for the specific scenario. This requires careful database configuration and application testing.
6
If the contention is on specific tables, investigate if database indexing can be improved to speed up read operations, thus reducing the window of conflict.
2. Implement Application-Level Concurrency Control medium
Introduce application logic to manage concurrent access to shared data, preventing simultaneous read and write operations on the same resources.
1
Identify the specific data objects or tables that are frequently involved in read/write conflicts. This often involves examining the error messages and the context in which they occur.
2
In the ABAP code, implement a mechanism to check for the existence of write operations before initiating a read, or vice-versa. This could involve a custom flag or a status field in a related table.
IF sy-batch = 'X'. " Example: If running in background, be more cautious
DATA: lv_lock_status TYPE c.
SELECT SINGLE lock_status INTO lv_lock_status FROM z_my_critical_table WHERE key_field = @wa_data-key_field.
IF lv_lock_status = 'W'. " 'W' for Write in progress
MESSAGE 'Data is currently being updated. Please try again later.' TYPE 'E'.
ELSE.
" Proceed with read operation
SELECT * FROM z_my_critical_table INTO @wa_data WHERE key_field = @wa_data-key_field.
" ... process data ...
ENDIF.
ELSE.
" Normal read operation
SELECT * FROM z_my_critical_table INTO @wa_data WHERE key_field = @wa_data-key_field.
" ... process data ...
ENDIF.3
Alternatively, use SAP's enqueue/dequeue mechanism more strategically. While `ENQUEUE` is typically for exclusive locks, it can be used to signal that a write operation is in progress, allowing other processes to wait or be notified.
DATA: lv_handle TYPE enqmode.
CALL FUNCTION 'ENQUEUE_E_LOCK_OBJ'
EXPORTING
mode_z_my_critical_table = 'E' " Exclusive lock for write
x_key_field = wa_data-key_field
EXCEPTIONS
foreign_lock = 1
system_failure = 2
OTHERS = 3.
IF sy-subrc <> 0.
MESSAGE 'Another user is modifying this record. Please wait.' TYPE 'E'.
ELSE.
" Perform write operation
UPDATE z_my_critical_table SET ... WHERE key_field = @wa_data-key_field.
CALL FUNCTION 'DEQUEUE_E_LOCK_OBJ'
EXPORTING
mode_z_my_critical_table = 'E'
x_key_field = wa_data-key_field.
ENDIF.4
Consider using a queuing mechanism for write operations if a high volume of concurrent updates is expected for specific data. This ensures writes are processed sequentially.
3. Adjust Database Isolation Levels (with caution) advanced
Modify the database transaction isolation level for specific transactions to allow concurrent reads and writes, understanding the implications.
1
Identify the specific database user or session that is encountering the error. This might require tracing the connection.
2
Understand SAP's default isolation levels and how they are managed. S/4HANA typically uses database-specific defaults, often optimized for performance.
3
If absolutely necessary, and after thorough analysis and testing, consider setting a lower isolation level for the problematic transaction. For example, in HANA, this could involve using `READ COMMITTED` or `READ COMMITTED NO WAIT`.
ALTER SESSION SET "databaselocks" = 'READ COMMITTED';4
Crucially, understand the implications of changing isolation levels. Lowering isolation can lead to phenomena like dirty reads, non-repeatable reads, and phantom reads, which can corrupt data if not handled carefully by the application.
5
This solution is generally not recommended as a primary fix and should only be considered for specific, well-understood scenarios where the application can tolerate the potential side effects or has implemented compensating logic.