Oracle

Meaning of “Disk Reads” Values in DBA_HIST_SQLSTAT

This post relates to my previous writing on mining the AWR. I noticed that it’s very easy to misinterpret the DISK_READS_TOTAL and DISK_READS_DELTA columns in DBA_HIST_SQLSTAT. Let’s see what the documentation says: DISK_READS_TOTAL – Cumulative number of disk reads for this child cursor DISK_READS_DELTA – Delta number of disk reads for this child cursor You…

Oracle Free Block Corruption – Test Case

My very first blog post at Pythian – Trick or Treat? So there I was, faced with more that 4000 block corruptions as shown from v$database_block_corruption. The script  corrupt_seg.sql identified the corruption as Free Block Corruption (block not associated with any segments). So how can free block corruption be removed? One method is to format the corrupted…

Mining the AWR to Identify Performance Trends

Sometimes it’s useful to check how performance of a SQL statement changes over time. The diagnostic pack features provide some really useful information to answer these questions. The data is there, but it not always easy to retrieve it, especially if you want to see how the performance changes over time. I’ve been using three really…

UDM is watching you, UDMs

With time monitoring of several thousand targets of different versions and on different operating systems accumulates additional checks and user-defined metrics for specific requirements. With the presence of a dozen super administrator accounts, the Oracle Enterprise Manager environment demands specific monitoring so that checks that were customized and configured for certain targets are not lost….

Linux HugePages for Oracle on Amazon EC2

One of the optimizations available to us when running Oracle on Linux is huge page support. This feature of the Linux kernel enables processes to allocate memory pages of size 2M (instead of 4k). In addition, memory allocated using hugepages is pinned in physical memory. It cannot be swapped out. It is now common practice…

Simple and Quick Way to Get SQL_ID of Query in Oracle

If you need to get SQL_ID of a query from a busy system, which has similar queries scattered all around, it becomes a hassle to get what you are looking for. If the query for which you are getting SQL_ID is big, or contains lots of apostrophes or other not-so-nice characters, then it becomes more…

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