为什么调度器链步骤名的最大长度是 24 个字节？

Question

我正在尝试创建一个 30 字节长的链步骤。它正在失败。

设置：

SQL> begin
  2      dbms_scheduler.create_program(
  3         program_name => lpad('A', 30, 'A')
  4       , program_type => 'PLSQL_BLOCK'
  5       , program_action => 'begin null; end;'
  6         );
  7      dbms_scheduler.create_chain('CHAIN_NAME');
  8  end;
  9  /

PL/SQL procedure successfully completed.

正在创建链步骤：

SQL> begin
  2      dbms_scheduler.define_chain_step(
  3          chain_name => 'CHAIN_NAME'
  4        , step_name => lpad('A', 30, 'B')
  5        , program_name => lpad('A', 30, 'A')
  6          );
  7  end;
  8  /
begin
*
ERROR at line 1:
ORA-27465: invalid value BBBBBBBBBBBBBBBBBBBBBBBBBBBBBA for attribute step_name
ORA-06512: at "SYS.DBMS_ISCHED", line 5057
ORA-06512: at "SYS.DBMS_ISCHED", line 1760
ORA-06512: at "SYS.DBMS_SCHEDULER", line 1786
ORA-06512: at line 2

我有一个字节语义数据库。

描述 DBA_SCHEDULER_CHAIN_STEPS STEP_NAME 的最大长度为 128 字节，即 32 个 4 字节 unicode 字符：

SQL> desc dba_scheduler_chain_steps;
 Name                                      Null?    Type
 ----------------------------------------- -------- --------------------
 OWNER                                     NOT NULL VARCHAR2(128)
 CHAIN_NAME                                NOT NULL VARCHAR2(128)
 STEP_NAME                                 NOT NULL VARCHAR2(128)
 ...

如果我查看 DBA_SCHEDULER_CHAIN_STEPS 的定义，那么 STEP_NAME 列来自 SYS.SCHEDULER$_STEP.VAR_NAME。该列的定义是：

SQL> select data_type, data_length, char_length, char_used
  2    from dba_tab_columns
  3   where owner = 'SYS'
  4     and table_name = 'SCHEDULER$_STEP'
  5     and column_name = 'VAR_NAME';

DATA_TYPE DATA_LENGTH CHAR_LENGTH C
--------- ----------- ----------- -
VARCHAR2          128         128 B

换句话说，对象名称的最大大小为 128 字节（32 个 Unicode 字符）。

Oracle 数据库管理员指南的

Section 29.2 "About Scheduler Objects and Their Naming" 说

Scheduler objects follow the naming rules for database objects exactly and share the SQL namespace with other database objects.

In other words

Names must be from 1 to 30 bytes long...

但是，如果我创建一个名称为 24 字节长和名称为 25 字节长的链步骤，则 24 字节的名称将成功，而 25 字节的名称将失败

SQL> begin
  2      dbms_scheduler.define_chain_step(
  3          chain_name => 'CHAIN_NAME'
  4        , step_name => lpad('A', 24, 'B')
  5        , program_name => lpad('A', 30, 'A')
  6          );
  7  end;
  8  /

PL/SQL procedure successfully completed.

SQL> begin
  2      dbms_scheduler.define_chain_step(
  3          chain_name => 'CHAIN_NAME'
  4        , step_name => lpad('A', 25, 'B')
  5        , program_name => lpad('A', 30, 'A')
  6          );
  7  end;
  8  /
begin
*
ERROR at line 1:
ORA-27465: invalid value BBBBBBBBBBBBBBBBBBBBBBBBA for attribute step_name
ORA-06512: at "SYS.DBMS_ISCHED", line 5057
ORA-06512: at "SYS.DBMS_ISCHED", line 1760
ORA-06512: at "SYS.DBMS_SCHEDULER", line 1786
ORA-06512: at line 2

:-(

为什么？这在任何地方都有记录吗？

Answer 1

根据MoS Doc ID 2246248.1：

This restriction of DBMS_SCHEDULER.define_chain_step attribute “step_name” is explicitly coded and confirmed by development.

-- Attribute 'step_name' cannot be longer than 24 characters or contain '.'

该文档仅引用 11.2.0.3，但它仍然在 12.1 和 12.2 中抛出错误。

这并不能真正解释为什么，但它有点记录...只是不在文档中。

为什么调度器链步骤名的最大长度是 24 个字节？

Why is the maximum length of a scheduler chain step name 24 bytes?

oracle

dbms-scheduler