Improved functionality for tablespace fast pre-allocation

My customer is experiencing huge performance problems due to Tablespace Pre-allocation (DB2_USE_FAST_PREALLOCATION).
At this time, IOCP Timeout occurs in Db2 and many tossbuffers occur in GPFS.
This customer has been struggling with this problem for a long time and wants Db2 to improve it.

Below are the cases that have been opened to find the cause.

TS012637554(a lot of IOCP Timeout occurring, 4/4/2023)
TS011724109(a lot of IOCP Timeout occurring after Db2 upgrade from v11.1.4.6 to v11.5.7.0, 1/5/2023)
TS011324928(Batch Job performance issue with IOCP Timeout, 11/23/2022)
TS011152607(Performance issue, 11/7/2022)
TS009302630(Many IOCP timeout messages occurred in the minutes, 5/10/2022)

While this IOCP timeout occurs, Db2 is almost in the Hang state, and sometimes this Hang state lasts more than 10 minutes.

So we have recommended the following two avoidance methods to our customer.

1. Turn DB2_USE_FAST_PREALLOCATION off
2. The workaround : create a large dummy table to remove sparese-ness during night time when workload is light. Then, drop the dummy table. Then, the space will be available for the real table.

Customer reluctants these two methods with following reasons.
For the #1, tablespace creation/resizing is very slow, and when creating or increasing the size of a tablespace, application delays will occur.
And when they change DB2_USE_FAST_PREALLOCATION=OFF, we don't know what side effect there will be. Furthermore, changing DB2_USE_FAST_PREALLOCATION requires a restart of Db2.

For the #2 Workaround, this is a burden to the customer. And it is difficult to predict how much dummy data to put in and when to do it.

So, I suggest the method below to improve this problem.

1. Db2 automatically performs initialization and formatting in the background for tablespace pages extended by Fast Pre-allocation.
  This will drastically reduce the occurrence of tossbuffer that occurs when data is first written to the expanded page.

2. Db2 allows the DB2_USE_FAST_PREALLOCATION option to be applied separately for each tablespace, and this should be easily changed with the ALTER TABLESPACE statement.
  Customers can change the options for the tablespaces they need when they need it, and we will be able to give our customers multiple choices.