Yesterday, I demonstrated a DataGuard Switchover from a 2node RAC(ASM) database to a SingleInstance(FileSystem) Database.
Quick and Rough Notes : Undo and RedoUndo is where Oracle logs how to reverse a transaction (one or more DMLs in a transaction)Redo is where Oracle logs how to replay a transactionUndo and Redo are written to as the transaction proceeds, not merely at the end of the transaction(imagine a transaction that consists of 1million single-row inserts, each distinct insert is written to undo and redo) Undo segmentsOracle dynamically creates and drops Undo segments depending on transaction volumeAn undo segment consists of multiple extents.
Here are some extracts from an 126.96.36.199 AWR Report I ran a simulated workload on this server for about 40minutes and generated this report.
In my previous blog post, I had demonstrated a few custom services created and started with DBMS_SERVICE.
My previous blogpost covered using ALTER SYSTEM/SESSION to set tracing for a specific SQL_ID that has been determined in advance.
So far, the previous examples have been on tracing the Execution of SQL statements and/or the Execution Plan used.
In the previous posts, I have traced eitherSELECTorINSERT or UPDATE or DELETEstatements I have pointed out that the block statistics are reported as “FETCH” statistics for SELECTs and “EXECUTE” statistics for the DMLs What if we have an INSERT … AS SELECT ?