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--- bugs_oracle [2018/05/29 11:20] – external edit 127.0.0.1
+++ bugs_oracle [2021/04/27 11:32] (current) – andonovj
@@ Line 1: / Line 1: @@
-  - **Wrong function extract**
+======Overview======
+Oracle is full of bugs, I am sorry to say it, but like any software, even Oracle has A LOT of bugs. Here are few of them:
+  - [[oracle_bugs_wrong_hour_extract| Incorrect hour extract]]
+  - [[oracle_bugs_statistic_advisor| Statistic Advisor]]
+  - [[oracle_linux7.2_crash|Crash due to Linux 7.2 IPC Setting]]
+  - [[oracle_12c_expdp_hang_enqueue_blocker|Expdp hangs/slow on Enqueue blocked on low memory]]
-Very interesting "Feature" which I was shown in oracle is the function "extract hour from timestamp", it appears that Oracle will provide an hour which is wrong:
-<sxh bash>
-select (extract (hour from current_timestamp)),current_timestamp from dual;
-(EXTRACT(HOURFROMCURRENT_TIMESTAMP)) CURRENT_TIMESTAMP
------------------------------------- -------------------
-                                    2017-11-14 10:44:00
-</sxh>
-**Solution**
-This behavior is somehow normal however, since the function: extract (hour from current_timestamp) is supposed to return you the hour in UTC format, excluding the timezone, therefore if the hour is 18:00 and the timezone is +02:00 it will return you 16:00, instead of 18:00. There are 2 ways how to negate this:
-   * **Use the current_scn**:
-<sxh bash>
-SQL> select (extract (hour from (scn_to_timestamp(current_scn)))) from v$database;
-(EXTRACT(HOURFROM(SCN_TO_TIMESTAMP(CURRENT_SCN))))
---------------------------------------------------
-SQL>
-</sxh>
-  * **Use the sum of the UPC hour and the time zone**:
-<sxh bash>
-SQL> Select (extract (HOUR from current_timestamp)), current_timestamp from dual; -------- We will extract the UTC value for hour
-SQL> Select (extract (HOUR from current_timestamp)) UTC_HOUR, (extract (TIMEZONE_HOUR from current_timestamp)) SESSION_TZ, (extract (HOUR from current_timestamp))+(extract (TIMEZONE_HOUR from current_timestamp)) SESSION_HOUR ,current_timestamp from dual;
-  UTC_HOUR SESSION_TZ SESSION_HOUR CURRENT_TIMESTAMP
----------- ---------- ------------ ---------------------------------------------------------------------------
-          1           17 16-NOV-17 17.26.55.236687 +01:00
-</sxh>