Infrastructure Catalogue

This is a list of articles I’ve written that get a little heavily into technical details and won’t necessarily be very helpful to the typical DBA or developer. Each entry has a date stamp and a short note of the contents. The articles are generally listed most-recent first.

• dbms_output (April 2024): you only see the output if your client calls dbms_output.get_lines(), and it uses the current array fetch size to do so.
• Querying LONGs (March 2024): They shouldn’t be there, but sometimes you can’t avoid them
• Disabling oradebug (March 2024): it is possible to block any calls to oradebug.
• SDU activity (December 2023): a follow up (or down) on the network activity below the SDU
  • DB_links & SDU_SIZE (July 2019): How the SDU_SIZE affects the way data travels across db_links.
• sys_op_descend() (November 2023): Expanded note on the effect of descending columns on index size
• XMLtype storage (Aug 2023): Investigating space requirements for compressed binary XMLtype – pt. 1
• Result Cache upgrade (Feb 2023): an enhancement to scalability in 21c
  • Result Cache threat (Sept 2015): Seeing other sessions’ temporary data
  • Result Cache threat 2 (Sept 2015): Incorrect usage means wrong results.
• Global Rowids (Feb 2023): a note describing how rowids are stored in global indexes
• Row Migration (Dec 2022): A basic rewrite of a note published in 2014, re-tested for 19.11
  • Row migration (Feb 2014): The original note, also pointing out the “deleted row” stubs left behind after each migration.
• Hakan Factor (Nov 2022): A detailed look at handling a problem with rows that grow significantly over time.
  • Seeing the Hakan Factor (May 2013): A sys-owned procedure to extract the Hakan factor from column tab$.spare1.
• Lost Space (Nov 2022): How dbms_space_admin fixed my bitmaps when dba_free_space “lost” some free space.
• Dumping redo (Sept 2022): a convenient method for minimising the redo you need to dump when testing a feature.
• Shrinking Indexes (Sept 2022): A lesson in comparing workloads – in this case index coalese vs. shrink space (with or without compact).
• Drop Partition (Aug 2022): the mechanics and cost of deferred global index maintenance
• ORA-00054 pt.1 (July 2022): Trouble-shooting with errorstack and ksq trace
  • ORA-00054 pt.2 (July 2022): Trouble-shooting with systemstate trace
• Why “lag() ignore nulls” is slow (May 2022): and how to work around the problem in some cases.
• dbms_redefinition defect (May 2022): using copy_table_dependencies() can produce metadata inconsistencies.
• Long v$ definitions (Mar 2022): Some definitions in v$fixed_view_definition are too long for the view. A workaround.
• X$ row sizes (Mar 2022): Simple script to get some clue about rows in x$ structures
• V$ cascade (Mar 2022): Why does is v$ a synonym for v_$ which is a view on v$
• Digging into x$ (Mar 2022): preliminary investigation of x$ information
• Session Count issue (Mar 2022): v$session, v$resource_limit and v$sysmetric don’t agree – digging in to x$
• Data Defaults (Feb 2021): a quirky little detail about how column defaults can be stored (and a point in favour of “commas at the ends of lines”).
• Pivot Cosmetics (Feb 2021): a minor change in the SQL*Plus output for a pivot that may require format updates in your code.
• Supplemental logging mess (Jan 2021): you need to be a little careful when you add supplemental logging clauses to a table.
• Check Constraints (Jan 2021): an odd difference in locking and waiting between disabling and enabling constraints.
• Naming side-effects (Dec 2020): How an upgrade that allows longer object names could break existing code.
• Dates and formats (Dec 2020): It’s important to use date datatypes, and check for type-conversion threats.
• Java Names upgrade (Dec 2020): how an upgrade from 12c to 19c caused an error in “home-grown” auditing.
• Row Sizes – pt.3 (Nov 2020): a little hackery to report the relative frequency of nulls in each column of a table.
  • Row sizes – pt2 (Oct 2012): a little hackery to generate code to show the patterns of Nulls in the rows of a table.
  • Row sizes – pt1 (Sep 2012): a little hackery to generate a “histogram” showing the distribution of row sizes in a table.
• Querying v$session (Oct 2019): a performance threat for large systems
• What’s my SID (Oct 2019): several ways of getting the SID (and some for the serial#)
• Dumping redo (June 2019): includes examples of how to be selective in dumping (online and archived) redo log records.
• Redo Op Codes (July 2017): my personal reference for translating redo op codes.
• Unpivot mechanics (June 2017): what does Oracle do internally to handle an unpivot?
• Optimising statspack (Oct 2016): some data dictionary / internal queries really do need good stats to avoid performance disasters.
• v$lock efficiency (May 2013): the benefit of collecting stats on individual x$ structures
• Hint error (Feb 2012): why is v$sql_shared_memory returning no data?
• Real-time Block Recovery (Dec 2010): How Oracle may handle blocks in the buffer cache that appear to have been corrupted
• Lock Modes (June 2010): my personal reference for translating numeric lock modes.
• SQL*Net Compression (May 2010): SQL*Net reduces data volume before transmitting it.
  • SQL*Net Compression pt. 2 (June 2013): How SQL*Net compression reduces “more data” waits, but not “roundtrip” counts.
• PGA Memory (June 2009): checking process memory and process memory detail.
• Oracle Pipes (Jan 2009): What’s currently inside a pipe created by dbms_pipe.