SQL/MX 2.x Reference Manual (G06.24+, H06.03+)

Introduction

HP NonStop SQL/MX Reference Manual—523725-004

1-6

Guardian User ID

Each user authorized to log on to a node is identified by a Guardian user ID that

consists of a group and user identification. The user ID has one of these forms:

group_number,user_number or

group_name.user_name

Guardian Super ID

Each node has one special user ID called the super ID that has Guardian group 255

and user number 255. The super ID has one of these forms:

255,255 or

SUPER.SUPER

The super ID can act as the owner of any object or file on the node.

Data Consistency and Access Options

Access options for DML statements affect the consistency of the data that your query

accesses.

For any DML statement, you specify access options by using the FOR option

ACCESS clause and, for a SELECT statement, by using this same clause, you can also

specify access options for individual tables referenced in the FROM clause.

The possible settings for option in a DML statement are:

The SQL/MX default access option for DML statements is READ COMMITTED.

However, you can set your system default for access options by specifying entries in

the SYSTEM_DEFAULTS table. See ISOLATION_LEVEL on page 10-44.

READ COMMITTED Specifies that the data accessed by the DML statement

must be from committed rows.

READ UNCOMMITTED

Specifies that the data accessed by the SELECT statement

need not be from committed rows.

SERIALIZABLE or

REPEATABLE READ

Specifies that the DML statement and any concurrent

process (accessing the same data) execute as if the

statement and the other process had run serially rather

than concurrently.

SKIP CONFLICT

Allows transactions to skip rows locked in a conflicting

mode by another transaction. SKIP CONFLICT cannot be

used in a SET TRANSACTION statement.

STABLE

Specifies that the row being accessed by the SELECT

statement is locked while it is processed, but concurrent

use of the database is allowed. STABLE is an ANSI

extension.