.
\nOn Twitter, Ludovico Caldara mentioned the #licensing #pitfall when using the Online Partition Move with Basic Compression. Those two features are available in Enterprise Edition without additional option, but when used together (moving online a compressed partition) they enable the usage of Advance Compression Option:
\n\nWill it be reflected in dba_feature_usage_statistics?
\n— Niels Jespersen (@njesp) April 19, 2020
\nAnd there was a qustion about detection of this feature. I’ll show how this is detected. Basically, the ALTER TABLE MOVE PARTITION sets the “fragment was compressed online” flag in TABPART$ or TABSUBPART$ when the segment was compressed during the online move.
I create a partitioned table:
\n\nSQL> create table SCOTT.DEMO(id,x) partition by hash(id) partitions 2 as select rownum,lpad('x',100,'x') from xmltable('1 to 1000');\n\nTable created.\nI set basic compression, which does not compress anything yet but only for future direct loads:
\n\nSQL> alter table SCOTT.DEMO modify partition for (42) compress;\n\nTable altered.\nI move without the ‘online’ keyword:
\n\nSQL> alter table SCOTT.DEMO move partition for (42);\n\nTable altered.\nThis does not enable the online compression flag (which is 0x2000000):
\n\nSQL> select obj#,dataobj#,part#,flags,to_char(flags,'FMXXXXXXXXXXXXX') from SYS.TABPART$ where obj# in ( select object_id from dba_objects where owner='SCOTT' and objec\nt_name='DEMO');\n\n OBJ# DATAOBJ# PART# FLAGS TO_CHAR(FLAGS,\n---------- ---------- ---------- ---------- --------------\n 75608 75608 1 0 0\n 75609 75610 2 18 12\nThe 0x12 is about the presence of statistics (the MOVE does online statistics gathering in 12c).
\n\nSQL> exec sys.dbms_feature_usage_internal.exec_db_usage_sampling(sysdate)\n\nPL/SQL procedure successfully completed.\n\nSQL> select name,detected_usages,currently_used,feature_info from dba_feature_usage_statistics where name='Segment Maintenance Online Compress';\n\nNAME DETECTED_USAGES CURRE FEATURE_INFO\n---------------------------------------- --------------- ----- --------------------------------------------------------------------------------\nSegment Maintenance Online Compress 0 FALSE\nNow moving online this compressed segment:
\n\nSQL> alter table SCOTT.DEMO move partition for (42) online;\n\nTable altered.\nThis has enabled the 0x2000000 flag:
\n\nSQL> select obj#,dataobj#,part#,flags,to_char(flags,'FMXXXXXXXXXXXXX') from SYS.TABPART$ where obj# in ( select object_id from dba_objects where owner='SCOTT' and objec\nt_name='DEMO');\n\n OBJ# DATAOBJ# PART# FLAGS TO_CHAR(FLAGS,\n---------- ---------- ---------- ---------- --------------\n 75608 75608 1 0 0\n 75611 75611 2 33554450 2000012\nAnd, of course, is logged by the feature usage detection:
\n\nSQL> exec sys.dbms_feature_usage_internal.exec_db_usage_sampling(sysdate)\n\nPL/SQL procedure successfully completed.\n\nSQL> select name,detected_usages,currently_used,feature_info from dba_feature_usage_statistics where name='Segment Maintenance Online Compress';\n\nNAME DETECTED_USAGES CURRE FEATURE_INFO\n---------------------------------------- --------------- ----- --------------------------------------------------------------------------------\nSegment Maintenance Online Compress 1 FALSE Partition Obj# list: 75611:\nThe FEATURE_INFO mentions the object_id for the concerned partitions (for the last detection only).
\nThe only way I know to disable this flag is to uncompress the partition, and this can be done online:
\n\nSQL> alter table SCOTT.DEMO move partition for (42) nocompress online;\n\nTable altered.\n\nSQL> select obj#,dataobj#,part#,flags,to_char(flags,'FMXXXXXXXXXXXXX') from SYS.TABPART$ where obj# in ( select object_id from dba_objects where owner='SCOTT' and object_name='DEMO');\n\n OBJ# DATAOBJ# PART# FLAGS TO_CHAR(FLAGS,\n---------- ---------- ---------- ---------- --------------\n 75608 75608 1 0 0\n 75618 75618 2 18 12\nAs a workaround, DBMS_REDEFINITION does not use the Advanced Compression Option. For example, this does not enable any flag:
\n\nSYS@CDB$ROOT>\nSYS@CDB$ROOT> alter table SCOTT.DEMO rename partition for (24) to PART1;\n\nTable altered.\n\nSYS@CDB$ROOT> create table SCOTT.DEMO_X for exchange with table SCOTT.DEMO;\n\nTable created.\n\nSYS@CDB$ROOT> alter table SCOTT.DEMO_X compress;\n\nTable altered.\n\nSYS@CDB$ROOT> exec dbms_redefinition.start_redef_table(uname=>'SCOTT',orig_table=>'DEMO',int_table=>'DEMO_X',part_name=>'PART1',options_flag=>dbms_redefinition.cons_use\n_rowid);\n\nPL/SQL procedure successfully completed.\n\nSYS@CDB$ROOT> exec dbms_redefinition.finish_redef_table(uname=>'SCOTT',orig_table=>'DEMO',int_table=>'DEMO_X',part_name=>'PART1');\n\nPL/SQL procedure successfully completed.\n\nSYS@CDB$ROOT> drop table SCOTT.DEMO_X; \nTable dropped.\n\nBut of course, the difference is that only the blocks that are direct-path inserted into the interim table are compressed. Not the online modifications.
\nAs far as I know, this is detected only for partitions and subpartitions, the online partition move operation which came in 12cR1. Since 12cR2 we can also move online a non-partitioned table and this, as far as I know, is not detected by dba_feature_usage_statistics. But don’t count on this as this may be considered as a bug which may be fixed one day.
\n", "protected": false } }