dbs/db4/parallel_alter_tables is a SAP Parameter attribute which is used to control Allow ALTER TABLE while INSERTS occur in parallel information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
dbs/db4/parallel_alter_tables profile paramerter attributes
Parameter Name: dbs/db4/parallel_alter_tables
Description: Allow ALTER TABLE while INSERTS occur in parallel
Default Value:
Parameter Type ( See
IF_PARAMETER_TYPES)
: String(STRING)
Restriction Values:
Parameter Unit:
Parameter Group: Database
CSN Component: BC-DB-DB4
System-Wide parameter: Yes
Dynamic Parameter: No
Vector Parameter: No
Has Sub-Parameters: No
Check Function Exists: No
Parameter documentation
See SAP Note 960392 for full details. The following is an excerpt from
the SAP note.
ALTER TABLE may require exclusive locks on a table. Continual activity
on the table may starve the ALTER TABLE request. For example, ALTER
activity may be frequent on partitioned tables in which partitions are
added and dropped.
The Parallel Alter feature actively monitors a definable set of tables
that need coordination; then intelligently schedules read, write and
alter operations to prevent alter starvation.
Setup>
Specify the profile parameter in the DEFAULT.PFL (see below)
End all>> >application server instances of the SAP
system
Delete SQL packages
Building the Profile Parameter>
Note: Allow us to help you!>
If you are considering using this feature, feel free to open a CSN
message to the BC-DB-DB4 queue and we'll work with you to build an
appropriate monitoring string.
The table(s) that need to be coordinated by must be specified via
profile parameter in
/usr/sap//sys/profile/DEFAULT.PFL
The profile parameter has the following format:
dbs/db4/parallel_alter_tables = = ,
etc..
Where: is the name of the table or view to be
monitored for coordination. can contain wildcards ?
and *. Where ? matches any one>> >single character,
and * matches many. LeTteR cAsE iS iGnOrEd.
Where: is an arbitrary name that specifies the name of
the lock. Multiple tables or views that resolve to the same <(>
<<)>LockGroup> are coordinated together. can contain
variables %n that correspond to the respective wildcard in <(>
<<)>TableName>.
Example:>>
dbs/db4/parallel_alter_tables = MYLOCK=MY*, YOURLOCK=YOUR*>
In this example, the parameter would coordinate all of "MY" tables
as one group, and all of "YOUR" tables as another.>
Example:>>
dbs/db4/parallel_alter_tables = Lock_%0 = ?*>
Here, the parameter value would coordinate all tables on the system,
using a equal to the first character of every table.
So tables SFLIGHT and SVERS would both resolve to Lock_S.>
Table views complicate the specification. Because the LIB_DBSL only
"sees" SQL text, views that reference "coordinated tables" must also be
listed in the profile parameter.
dbs/db4/parallel_alter_tables = LOCK_%0=*TABLE, LOCK_%0=*VIEW
Would put all tables and views that start with the same prefix and that
end either on TABLE or on VIEW into the same lock group. So MYAPPTABLE
and MYAPPVIEW are coordinated together because they have a lock name of
LOCK_MYAPP.
When active, the developer trace shows (for example):
C parallel_alter_tables = LOCK_%0=*TABLE C = LOCK_%0=*VIEW>
See SAP Parameter Documentation for full SAP documentation for this profile parameter.