Is there a way to examine the contents of a SAP HANADB transaction log

I have a SAP B1 system that's being migrated from Microsoft SQL to HANA DB. Our solution in the staging environment is producing huge transaction logs, tens of gigabytes in an hour, but the system isn't receiving production workloads yet. SAP have indicated that the database is fine, and that it's our software that's at fault, but I'm not clear on how to identify this. As far as I can tell each program is sleeping between poll intervals, and the intervals are not high (one query per minute). We just Traced SQL for an hour, and there were only in the region of 700 updates, but still tens of gigabytes of transaction log.

Does anybody have an idea how to debug the transaction log? - I'd like to see what's being recorded.


1 answer

  • answered 2021-06-10 23:30 Lars Br.

    The main driver of high transaction log data is not the number of SQL commands executed but the size/number of records affected by those commands.

    In addition to DML commands (DELETE/INSERT/UPDATE) also DDL commands like CREATE and ALTER table produce redo log data. For example, re-partitioning a large table will produce a large volume of redo logs.

    For HANA there are tools (hdblogdiag) that allow inspecting the log volume structures. However, the usage and output of this (and similar tools) absolutely require extensive knowledge of the internals of how HANA operates redo logs.

    For the OPs situation, I recommend checking for the volume of data changes caused by both DML and DDL.